Wednesday

July 1, 2015

July 1, 2015

Number of results: 20,715

**Chemistry**

Give the enthalpy change and entropy change values shown below calculate the free energy change for this reaction at 25 degrees C using Gibbs free energy equation. How does this value compare to the free energy change using the standard free energy of formation data? delta H=-...
*May 16, 2007 by Christian*

**Chemistry**

how many Kj of heat are evolved when 6g of pure carbon is completely burned? how many grams of carbon must be burned to furnish 39.3 kJ of heat. enthalpy of combustion of carbon is -393.5
*November 24, 2014 by Shabana*

**chemistry**

A 10.0 g sample of liquid gallium metal, at its melting point, is added to 50.0g of water. The initital temperature of the water is 24.0 degrees C. If the molar enthalpy of freezing gallium is -5.54 kj/mol, what is the final temperature of the water? Thanks
*November 7, 2010 by Bob*

**Chemistry**

For a particular isomer of C8H18, the following reaction produces 5099.5 kJ of heat per mole of C8H18(g) consumed, under standard conditions. What is the standard enthalpy of formation of this isomer of C8H18(g)?
*November 3, 2014 by Z*

**chemistry**

calculate the Ph of 0.3 M sodium propanoate, Ka 2.0 x 10 base -3. then calculate the pH after 0.03 mol NCL is added to 2L of the first solution.
*July 20, 2013 by Mandy*

**Math**

Measurements: Length = 5 cm Width = 18 cm Height = 26 cm ____________________________________________ Calculate the surface area of the prism. Formula: Calculate the volume of the prism Formula: Calculate the volume of the prism as if it were a pyramid. Formula: P.S. I have ...
*February 25, 2013 by Jman*

**chem30**

what is the molar enthalpy of combustion for magnesium? calimetry experiment results 100.0ml of HCl with 0.31g of Mg ribbon temp before ribbon added 23degrees and after ribbon added 37degrees. Need to show work so I understand. q=mcdeltaT
*March 7, 2013 by redeye*

**Physics**

Two crates, of mass m1 = 60 kg and m2 = 130 kg, are in contact and at rest on a horizontal surface (Fig. 4-54). A 620 N force is exerted on the 60 kg crate. The coefficient of kinetic friction is 0.15 a)Calculate the acceleration of the system. b) calculate the force that each...
*October 11, 2010 by Syl*

**Chemistry**

1)A buffer solution that is 0.10 M sodium acetate and 0.20 M acetic acid is prepared. Calculate the initial pH of this solution. The Ka for CH3COOH is 1.8 x 10-5 M. As usual, report pH to 2 decimal places. *A buffered solution resists a change in pH.* 2)Calculate the pH when ...
*March 10, 2015 by JUNDY*

**Chemistry**

1)A buffer solution that is 0.10 M sodium acetate and 0.20 M acetic acid is prepared. Calculate the initial pH of this solution. The Ka for CH3COOH is 1.8 x 10-5 M. As usual, report pH to 2 decimal places. *A buffered solution resists a change in pH.* 2)Calculate the pH when ...
*March 10, 2015 by JUNDY*

**Calculus 3**

Let u=j+k and v=i+jsqrt2. a) Calculate the length of the projection of v in the u direction. b) Calculate the cosine of the angle between u and v. Your help is very much appreciated!
*January 16, 2013 by Heather*

**Chemistry**

Calculate the following temperatures 1. Its 18 F. What is this in C? 2. Calculate this temperature (from question #1) to K 3. Convert 38.2 C to F My answers 1. -7.7 C 2. 265.3 K 3. 100.76 F Let me know what I did wrong if I'm incorrect thank you :)
*January 26, 2015 by Clare*

**CHEM. help please**

2 H2O (l) → 2 H2 (g) + O2 (g) 1. Without doing any calculations, which side will enthalpy favor in this reaction? Entropy? 2. What volume of water in gallons would need to be split to store the same amount of energy as found in 10.0 gallons of gasoline? (Gasoline ...
*November 2, 2010 by Andrew*

**chemistry**

Use bond energies to predict the molar enthalpy of combustion of acetylene gas. 2C2H2 + 5O2--> 4CO2 + 2H2O I am confused as to how to do the 2C2H2 in relation to the bonds? how many c-c bonds would there be, or would they be triple bonds?
*October 11, 2010 by ben*

**Thermodynamics**

5 pounds of an ideal gas with R=38.7 and K=1.668 have 300Btu of heat added during a reversible constant pressure change of state, initial temperature=80°F. Determine: a.)the final temperature b.)change of internal energy change of enthalpy change of entropy
*March 6, 2010 by Janus*

**Chemistry**

Consider the following two thermochemical equations N2+2.5O2-> N2O5(s) Delta H=xkJ N2+2.5O2-> N2O5(g) Delta H=ykJ The enthalpy change in kJ for the sublimation of one mole of N205 solid to gas would be represented by the quantity a)x+y b)x-y c)y-x d)-x-y Assuming it's a)
*July 24, 2010 by Bob*

**physics**

A 64 kg hiker climbs to the top of a 3700 m-high mountain. The climb is made in 5.5 h starting at an elevation of 2900 m. Calculate the average power output in watts. Calculate the average power output in horsepower & Calculate assuming the body is 14% efficient, what rate of ...
*October 10, 2010 by mike*

**chemistry**

Given the following reactions Fe2O3(s) + 3CO (s) → 2Fe (s) + 3CO2(g)ΔH =-28.0 kJ 3Fe (s) + 4CO2(s) → 4CO (g) +Fe3O4(s) ΔH = +12.5 kJ the enthalpy of the reaction of Fe2O3 with CO 3Fe2O3(s) + CO (g) → CO2(g) + 2Fe3O4(s) is __________ kJ
*November 2, 2014 by Anonymous*

**college physics**

a toy cannon fires a projectile from ground level with a speed of 15.0 m/s, at an angle of 30.0 degrees above the horizontal. a) calculate the horizontal range of projectile. R=Vi^2/g * sin 2theta = (150/9.8)*(sin(2*30.0) = 19.88m I know this part is right but i'm not sure ...
*October 3, 2012 by toor*

**chemistry**

Hi, The problem is: "Calculate the concentration of OH- and the pH value of an aqueous solution in which [H30+] is 0.014M at 25C. Is this solution acidic, basic, or neutral?" I have calculated the OH- concentration to be: 7.1 X 10^-14 When I calculate the pH (using H30+), I ...
*March 30, 2011 by LaurenM*

**To Ms. Sue**

How do I calculate how much grain is required to feed you through the chicken you ate for dinner? And is it necessary to really try and calculate it?
*July 14, 2009 by devon*

**Chemistry**

Commercial vinegar usually has a concentration of 5%, per volume. a) Calculate the [H3O+] , if the density of acetic acid is 1.051 g/mL. b) Calculate the pH.
*May 13, 2012 by Andrea*

**physics**

a jet plane traveling at +87 m/s lands on a runway and comes to ret in 11 s. a)Calculate its uniform acceleration b)Calculate the distance it travels
*November 6, 2012 by charlie*

**physics**

a jet plane traveling at +87 m/s lands on a runway and comes to rest in 11 s. a)Calculate its uniform acceleration b)Calculate the distance it travels
*November 6, 2012 by kayla*

**Chemistry**

In the titration of 20.00 mL of 0.175 M NaOH, calculate the number of milliliters of 0.200 M HCl that must be added to reach a pH of 12,55. I know the answer is 11,9 mL but I don't know how to calculate it.
*November 22, 2013 by Helga*

**physics**

The system is frictionless and the trolley accelerates to the left at 3m/s squared. (a) calculate the unknown mass M. (b) calculate the magnitude of the forces in each string.
*March 15, 2015 by kulani*

**chemistry**

Calculate ∆T for the reaction. Assume the initial temperature of both reactants is 25.0◦C. Calculate the volume of the reaction mixture. Calculate the mass of the reaction mixture. Assume the density of the mixture is 1.03 g mL^(-1). Calculate the heat transferred ...
*October 22, 2014 by Anonymous*

**Enthalpy of Formation**

N2H4(g) + H2(g)--> 2 NH3(g) H1 = –1876kJ 3 H2(g) + N2(g)--> 2 NH3(g) H2 = –922 kJ The H.f for the formation of hydrazine: 2 H2(g) + N2(g)--> N2H4(g) will be______kj/mol I am very confused here. I thought I would just add H1 and H2 and divide by the molar mass of N2H4...
*May 16, 2010 by CHem*

**chemistry**

CH3OH CO + 2H2 H = +90.7kJ 9. For the forward reaction, is heat being absorbed or released? 10. How much heat would be transferred if 45.0 g of CH3OH is decomposed? 11. What quantity of CH3OH decomposition would lead to an enthalpy change of 18.5 kJ
*May 11, 2011 by Anonymous*

**chemistry**

CH3OH CO + 2H2 H = +90.7kJ 9. For the forward reaction, is heat being absorbed or released? 10. How much heat would be transferred if 45.0 g of CH3OH is decomposed? 11. What quantity of CH3OH decomposition would lead to an enthalpy change of 18.5 kJ
*May 11, 2011 by Anonymous*

**Chemistry**

Pentane is a small liquid hydrocarbon, between propane and gasoline in size C5H12. The density of pentane is 0.626g/ml and its enthalpy of combustion is ΔHcomb =-3535kj/mol. Estimate the fuel valve and the fuel density of pentane.
*November 8, 2012 by Brittany*

**chemistry**

The reaction SO2 + H2O =H2SO4 Is the last step in the commercial production of sulfuric acid . the enthalpy change for this reaction is -227 KJ . In designing a sulfuric acid plant is it necessary to provide for heating or cooling of the reaction mixture ? explain
*November 12, 2014 by mathew*

**Thermochemistry**

A constant pressure calorimeter having a heat capacity of 60.8 kJ/K is used to measure the energy released from burning a compound in excess oxygen to form CO2(g) and H2O(l). If the enthalpy of combustion of the compound is -2914.0 kJ/mol and the temperature of the calorimeter...
*December 4, 2011 by LaurenB*

**Lauren**

The amount of heat required to raise temperature of 55.85 g of iron 1 degrees C is called its A. Change of energy B. Enthalpy C. Molar heat capacity D. Specific heat capacity E. Specific Heat.
*November 16, 2007 by Chemistry*

**Chemistry**

Indicate whether Delta S and Delta H is positive or negative. Then indicate if the reaction is entropy driven, enthalpy driven or neither. NaCl(s) + H2O(l) + Heat => NaCl (aq)
*September 19, 2008 by Yuval*

**UCF**

What will be the change in enthalpy when 100.0 g of butane, C4H10, is burned in oxygen as shown in the thermochemical equation below? 2 C4H10(l) + 13 O2(g) → 8 CO2(g) + 10 H2O(g) ΔH = −5271 kJ −2636 kJ −4534 kJ −9087 kJ −1.817 × 104 kJ
*April 2, 2014 by Alex*

**physics**

For a helium atom containing two protons, two neutrons and two electrons: A)Calculate the first energy levels(n=1,2,3,4,5)(answers (-54.4eV, -6.04eV, -3.4eV, -2.176eV) b)Calculate the frequency in Hz of a proton emitted from n=2 to n=1 (answer 9.86x 10^15Hz) c)calculate the ...
*December 4, 2012 by chanty*

**college chemistry**

the normal freezing point of the element mercury, Hg(l), is a -38.9°C and its molar enthalpy of fusion, ΔHfusion=2.29 KJ/mol. What is the entropy change (J/K) of the system when 50 g of Hg(l) freezes at the normal freezing point. Hg= 200.59 g/mol
*December 6, 2010 by Jamaal *

**Chemistry**

Substance A has a normal fusion point of ‑10.0 oC, an enthalpy of fusion = 150.0 J g^-1; specific heats for the solid and the liquid are 3.00 and 6.20 J g^-1 oC^-1, respectively. How much heat, in J, is required to change 150 grams of A from a solid at –40.0 oC to a ...
*November 8, 2011 by Kale*

**chemistry**

Ethanol (C2H5OH) melts at -114 °C. The enthalpy of fusion is 5.02 kJ/mol. The specific heats of solid and liquid ethanol are 0.97 J/g-K and 2.3 J/g-K, respectively. How much heat (kJ) is needed to convert 25.0 g of solid ethanol at -135 °C to liquid ethanol at -50 °C?
*February 3, 2012 by Anonymous*

**Thermodynamics**

A turbine operating under steady flow conditions receives steam at the following state: pressure 13.8 bar, specific volume 0.143 m^3/kg, specific internal energy 2591kJ/kg and velocity 30m/s. The state of steam leaving the turbine is as follows: pressure 0.35 bar, specific ...
*June 3, 2010 by Claire*

**Chemistry**

A zinc-copper battery is constructed as follows at 25°C. Zn|Zn^2+ (0.15 M)||Cu2+(3.00 M)|Cu The mass of each electrode is 200. g. a) Calculate the cell potential when this battery is first connected. - i got this to be 1.14V b.) Calculate the cell potential after 10.0 A of ...
*April 28, 2011 by Pamela*

**Chemistry**

Calculate the pH of a 50.0 mL solution 0.0120 M ethylaminium chloride (C2H5NH3Cl ) and 0.0360 M ethylamine C2H5NH2. Kb = 4.3 x 10-4 Calculate the pH when 5.0 mL of 0.1 M HI is added. Ignore any changes in the volume
*April 17, 2013 by m*

**Chemistry**

I have two questions that I do not know how to answer. Thanks for your help! 1. Calculate the [OH^-], [H^+], pH, and pOH for a 0.50M solution of CN^- 2. Calculate the molar solubility of PbCl2 in 0.40M KCl
*January 11, 2015 by Liz*

**Chemistry**

Consider the following two thermochemical equations N2+2.5O2-> N2O5(s) Delta H=xkJ N2+2.5O2-> N2O5(g) Delta H=ykJ The enthalpy change in kJ for the sublimation of one mole of N205 solid to gas would be represented by the quantity a)x+y b)x-y c)y-x d)-x-y I am thinking it...
*July 25, 2010 by Bobz*

**Chemistry**

Neat pure ethanol C2H5OH has an enthalpy of vaporization of 39.3 Kj/mol, and a vapor pressure of 0.308 atm at 50 C. What is the boiling point, at atmospheric pressure of 1 atm, of a solution consisting of 35 G of phenol (a non-electrolyte hydrocarbon with a molecular formula ...
*April 30, 2012 by Mima*

**chemistry**

The enthalpy change for the reaction below at 25oC is -2,252 kJ (per mole of C11H24). What is the internal energy change for the reaction at 25oC? 11 CO(g) + 23 H2(g) --> C11H24(l) + 11 H2O(l)
*November 3, 2014 by Sasha*

**physics university**

For a helium atom containing two protons, two neutrons and two electrons: A)Calculate the first energy levels(n=1,2,3,4,5)(answers (-54.4eV, -6.04eV, -3.4eV, -2.176eV) b)Calculate the frequency in Hz of a proton emitted from n=2 to n=1 (answer 9.86x 10^15Hz) c)calculate the ...
*December 3, 2012 by chanty*

**HOW TO CALCULATE LASS WIDTHS?**

can someone tell me how to calculate class width. suppose the number of classes and class widh being 5 and 12 respectively.form a grouped frequency distribution.. the maximum is 98 while the minimum is 12. Should i calculate it: maximum - minimum that is 98-12=76 to know how ...
*April 22, 2012 by PALLAVI*

**Chemistry**

The vapor pressure of the liquid HF is measured at different temperatures. The following vapor pressure data are obtained. Temperature(K) Pressure mmHg 250 129.63 260 206.65 270 318.22 280 475.16 Determine the enthalpy of vaporization. I have know idea how to start this. Thank...
*February 7, 2012 by Hannah*

**Chemistry**

A 5.0g KBr sample, at 25 degrees celsius, dissolved in 25 ml of water, also at 25 degrees celsius. the final equilibrium temperature of the resulting solution is 18.1 degrees celsius, What is the enthalpy change in J/g and KJ/mole of KBr.
*November 14, 2012 by jonathan*

**Chemistry**

Determine how many mL of solution A (acetic acid-indicator solution) must be added to solution B (sodium acetate-indicator solution) to obtain a buffer solution that is equimolar in acetate and acetic acid. Solution A: 10.0 mL 3.0e-4M bromescol green solution 25.0mL 1.60M ...
*October 29, 2012 by Jake*

**Physics**

A 125 kg fullback is running at 5.0 m/s to the east and is stopped in 0.75 s by a head-on tackle by a tackler running due west. a) Calculate the original momentum of the fullback. i did this and got 625 kg- m/s b) Calculate the impulse exerted on the fullback i did this and ...
*October 31, 2009 by Jen *

**chemistry**

Can one calculate the number of moles of air? If so, calculate the number of moles in 1 kg of air (making sure your calculation, units and assumptions are fully explained); If not, explain why it is not possible to calculate the number of moles of air.
*August 7, 2013 by sarah*

**CHEMISTRY**

A mixture contains 5.00 g each of O2, N2, CO2, and Ne gas. Calculate the volume of this mixture at STP. Calculate the partial pressure of each gas in the mixture at STP. How do you calculate the mole fraction of each gas?
*May 11, 2010 by ~anonymous*

**Chemistry**

A 5.0-g Sample of KBr at 25.0 degrees celsius dissolves 25.0 mL of water also at 25.0 degrees celsius. The final equilibrium temperature of the resulting soltution is 18.1 degrees celsius. What is the enthalpy of of solution in kilojoules per mole of KBr?
*March 20, 2013 by Sam*

**Chem 2 enthalpy**

How much heat is evolved when 25.5 g of benzene freezes at 5.5 Celcius (molar heat of fusion is 9.94 kJ/mol and molar mass of benzene= 78.0 g/mol)
*August 26, 2010 by Anonymous*

**Thermochemistry**

When 1.477 mole of an inorganic salt were dissolved in 1.00 L of water in a constant pressure solution calorimeter, the temperature of the calorimeter changed from 25.00oC to 24.40 oC. The total heat capacity of the calorimeter including all its contents was 2.18 kJ oC-1 What ...
*June 12, 2009 by Douglas*

**chem**

assuming you have o.4g of Y(OH)3, calculate the mass of BaO2 required to react stoichiometrically to produce YBa2Cu3O7. Now calculate the mass of CuO. Please HELP! Write the balanced equation. Then, calculate the moles of Y hydroxide from .4 g. Then, notice from the balanced ...
*October 24, 2006 by nick*

**apchem**

A 15.0g sample of liquid ethanol, C2H5OH, absorbs 5.13x10^3 J of heat at its normal boiling point, 78.0C. The molar enthalpy of vaporization of ethanol is 39.3kJ/mol. (a) What volume of ethanol vapor is produced? The voume is measured at 78.0C and 1.00atm pressure. (b) What ...
*January 27, 2008 by alk*

**Chemistry**

A 15.0g sample of liquid ethanol, C2H5OH, absorbs 5.13x10^3 J of heat at its normal boiling point, 78.0C. The molar enthalpy of vaporization of ethanol is 39.3kJ/mol. (a) What volume of ethanol vapor is produced? The voume is measured at 78.0C and 1.00atm pressure. (b) What ...
*January 27, 2008 by David*

**Chemistry**

A titration is performed by adding .600 M KOH to 40.0 mL of .800 M HCl. Calculate the pH before addition of any KOH. Calculate the pH after the addition of 5.0 mL of the base. Calculate the volume of base needed to reach the equivalence point. What is the pH at the equivalence...
*April 1, 2011 by Summer*

**Chemistry**

Calculate the H+ for number #2 #2 : H+ = 10^-2, with a pH of 2 Not sure how to calculate H+
*April 29, 2015 by Clare*

**Inorganic chemistry**

The thermochemical equation for the combustion of hexane is shown below. C6H14(g) + 19/2Os(g) ==> 6CO2(g) + 7H2O(g) Delta H = -4163kJ What is the enthalpy change for the combustion of 2.50g C6H14? 2.50 g/86g = .029 mol -4163kJ/.029 = -1.43 x 10^5kJ
*May 12, 2009 by Steve*

**Math**

Julie is conducting an experiment where she placed 29.5 mL of water in a calorimeter at 15.0 °C. Then, 2.4 g of A (molar mass = 48.0 g/mol), also at 15.0°C, is added to the water in the calorimeter and the temperature of the solution increases to 28.0 °C. The following ...
*October 5, 2014 by Kelly*

**Chemistry - General, Hess's Law**

In an experiment, 11.6g of a salt was dissolved in 100.0ml of water contained in the above calorimeter, all at an initial tmperature of 24.5 degrees Celsius. After dissolution was complete, the temperatur was 31.8C. The specific heat of the solution is 3.63J/gxC and the ...
*July 24, 2009 by Sahar*

**Chemistry**

Explain why the absolute values of the standard enthalpy change in the reaction and heat measured by the calorimeter are not equal. Assume that there are no measurement errors of any kind. In the previous problem I solved that Delta H rxn was -1500 and q = 1.519 x 10^6 J and I...
*March 17, 2012 by David*

**Chemistry LAB 1**

What is the Molar Enthalpy of Neutralization in kJ/mol if 5.00 moles of HCl(aq) (acid) neutralized 5.00 moles of NaOH(aq) (base) and released 6649J of heat? *Make sure you report your answer using the correct sign* DrBob222 gave me some help and I worked it out and got 1329.8 ...
*November 6, 2013 by BRANDIE*

**Chemistry**

The net reaction for fusion on a star like our Sun is: 4H(1,1) ==> He(4,2) + 2e(0,+1) Calculate the mass defect for this reaction. If one atom of He is formed this way, calculate the energy released. If one Kg of He is formed, calculate the energy released. The masses of ...
*March 16, 2014 by Jay*

**science-chemistry **

please anwser soon, a rigid 4.10L flask contains a mixture of 1.25 moles of H2, 0.250 mole of O2, and sufficient Ar so that the partial pressure of Ar in the flask is 1.00 atm. The temperature is 63.5 degrees C A) Calculate the total pressure in the flask B) calculate the mole...
*April 29, 2012 by Bryan*

**Chemistry**

H2O(l) = H2O(g) deltaHvap = + 40.7kJ shows the change in enthalpy when 1mol of liquid water vaporizes into water vapor. This is called the molar heat of vaporization. Given this information which is the proper value for the molar heat of condensation?
*April 5, 2010 by Tori*

**Chemistry**

The phrase “the heat absorbed or released by a system undergoing a physical or chemical change at constant pressure” is a. the change in enthalpy of the system. b. the change in internal energy of the system. c. the definition of a state function. d. the temperature change of ...
*July 2, 2013 by Jessica*

**Chem**

A gas is compressed from 73.7 L to 1.9 L at 0.70 atmospheres? In addition a total of 4400 J of heat are gained from warmer surroundings. What is the change in internal energy in kJ? I have a general idea of how to do this, but I tried and got -2851.8, which isn't right. What ...
*October 19, 2012 by Anonymous*

**chemistry - quant.**

I need help calculating the pH of a solution that is .0400M Na3AsO4 I was trying to calculate the pH with [H30+]=sqrt(ka1*ka2) What is the correct way to calculate this? Thankyou
*December 13, 2007 by anon*

**chem**

The combustion of hydrogen–oxygen mixtures is used to produce very high temperatures (approximately 2500 °C) needed for certain types of welding operations. Consider the reaction to be H2(g) + 1/2O2(g) --> H20(l) Standard enthalpy is -241.8kj What is the quantity of heat ...
*October 3, 2008 by tomi*

**physics**

A 5.40 Kg package slides 1.47 meters down a long ramp that is inclined at 11.6 degress below the horizontal. The coefficient of kinetic friction between the package and the ramp is = 0.313. Calculate the work done on the package by friction. Calculate the work done on the ...
*December 3, 2012 by clariza gonzalez*

**physics**

A bowling ball of mass 7.45 kg is rolling at 2.56 m/s along a level surface. (a) Calculate the ball's translational kinetic energy. J (b) Calculate the ball's rotational kinetic energy. J (c) Calculate the ball's total kinetic energy. J (d) How much work would have to be done ...
*March 6, 2015 by alba*

**Physics **

A bowling ball of mass 7.45 kg is rolling at 2.56 m/s along a level surface. (a) Calculate the ball's translational kinetic energy. J (b) Calculate the ball's rotational kinetic energy. J (c) Calculate the ball's total kinetic energy. J (d) How much work would have to be done ...
*March 6, 2015 by Yesica *

**physics**

A bowling ball of mass 7.45 kg is rolling at 2.56 m/s along a level surface. (a) Calculate the ball's translational kinetic energy. J (b) Calculate the ball's rotational kinetic energy. J (c) Calculate the ball's total kinetic energy. J (d) How much work would have to be done ...
*March 19, 2015 by alba*

**Physics**

A motorboat is traveling 5m/s East, and encounters a current traveling 2.5m/s, North. If the witdth of the river is 80m wide, how much time does it take the boat to reach the other shore. I understand how to calculate the resulatant velocity, but I dont understand why you use ...
*October 20, 2010 by Jennifer *

**chemistry**

The enthalpy change for the solution process when solid sodium hydroxide dissolves in water is -44.4 kJ/mol. When a 13.6 g sample of NaOH dissolves in 250.0 g of water in a coffee-cup calorimeter, the temperature increases from 23.0 o C to __________ o C. Assume that the ...
*November 15, 2010 by Anonymous*

**Science**

Write the formula, substitute numbers and units(labels)Mike mixed 20g of 60C water with 40g of 25C water. The final temperature was 39C. 1.Calculate the change of temperature for hot water. 2.Calculate the calories transferred from the hot water. 3.Calculate the amount of heat...
*March 29, 2010 by Jamie*

**Chemistry**

Caluclate the delta H for this reaction using standard enthalpies of formation. (The standard enthalpy of formation of liquid pentane is -146.8kJ/mol. Balanced equation balanced equation: C5H12(l)+8O2(g)-->5CO2+6H2O(g) CO2=393.5 H2O=40.7
*December 4, 2010 by Ashley*

**thermodynamics**

A scuba tank contains 1.5 kg. of air. The air in the tank is initially at 15 degree celcius. The tank is left near an engine exhaust line, and the tank's pressure doubles. Determine the final temperature, change of internal energy, change of enthalpy, and heat.
*November 29, 2011 by hermie*

**Hudson**

In a calorimetric experiment, 6.48 grams of lithium hydroxide was dissolved in water. The temp of the calorimeter rose from 25 celcius to 36.66 celcius. What is the molar change in enthalpy for this procces? LiOH(s) -> Li(aq) + OH (aq) (the heat capacity of the calorimeter ...
*October 8, 2012 by k-dawg*

**chemistry**

for a particular isomer C8H18, the following reaction produces 5113.3 kj of heat per mole of C8H18 consumed under standard conditions c8h18(g) + 25/2 O2 (g) ---> 8co2(g) + 9h2o(g) what is the standard enthalpy of formation of this isomer of c8h18? o2= 0 co2(g)= -393.5 h2o(g...
*June 19, 2013 by Annie*

**chemistry**

2. If the accepted enthalpy change value for the dissolving of sodium hydroxide in water is −44.2 kilojoules per mole, determine the percent error of the experimental value that you calculated in Part I. Show your work. (experimental - actual value) / actual value × 100 %
*July 18, 2013 by yuppp*

**Chemistry**

I just did an experiment on the enthalpy of combustion of different alcohols, and for my report, I've written that the condition of the wick is a source of random error, but i can't seem to explain it. I've written that it affects the rate of burning of the flame, and the heat...
*April 7, 2009 by TP*

**Chemistry**

Dr.Bob, this is regarding to the enthalpy posts.... I don't understand why you just switch it to negative??How do you know that it is neg???? I thought it started out neg though the problem does not give the number.... I am sorry,but I am a very slow learner...thank you for ...
*November 15, 2013 by Anonymous*

**Chemistry -please help!**

A zinc-copper battery is constructed as follows at 25°C. Zn|Zn^2+ (0.15 M)||Cu2+(3.00 M)|Cu The mass of each electrode is 200. g. a) Calculate the cell potential when this battery is first connected. - i got this to be 1.14V b.) Calculate the cell potential after 10.0 A of ...
*April 28, 2011 by Mandy*

**Chem**

(a) The molar solubility of Ag2CrO4(s) at 35°C is 1.3 10-4 mol/L. Calculate Ksp. (b) If 0.0490 g of AgIO3 dissolves per liter of solution, calculate the solubility-product constant. (c) Using the appropriate Ksp value from Appendix D, calculate the solubility of Cu(OH)2 in ...
*April 27, 2011 by Rebekah*

**physics**

A resistor (R = 900 ), a capacitor (C = 0.25 µF), and an inductor (L = 2.0 H) are connected in series across a 240 Hz AC source for which Vmax = 140 V. Calculate values for the following. ---I only need help with part c---- c) the phase angle between the current and voltage ...
*August 5, 2007 by asmi*

**phys**

An airplane is heading due south at a speed of 590 km/h. If a wind begins blowing from the southwest at a speed of 65.0 km/h (average). Calculate magnitude of the plane's velocity, relative to the ground. Calculate direction of the plane's velocity, relative to the ground. ...
*September 15, 2009 by physics*

**Chemistry**

Lead has a melting point of 327ºC, its specific heat is J/g•deg, and its molar enthalpy of fusion is 4.80 kJ/mol. How much heat, in kilojoules, will be required to heat a 500.0-g sample of lead from 23.0ºC to its melting point and then melt it?
*November 4, 2012 by steph*

**Chemistry**

Lead has a melting point of 327ºC, its specific heat is J/g•deg, and its molar enthalpy of fusion is 4.80 kJ/mol. How much heat, in kilojoules, will be required to heat a 500.0-g sample of lead from 23.0ºC to its melting point and then melt it?
*November 4, 2012 by steph*

**chemistry**

The normal boiling point of ethanol is 78.5C. Using the following information: delta H formation (C2H5OH (g))= -234.38 kJ/mol determine the enthalpy of vaporization of ethanol. I know it should be around 39.3 according to a table in my textbook, however, I don't know how to ...
*July 18, 2012 by Kellie*

**molarity**

calculate the molarity of k+ in a soln prepared by adding .2L of .200M K3PO4 and 75.0mL of .5M K3PO4. assume volumes are additive. A few of steps here and more than one way to answer the problem You need to calculate the total number of moles of K3PO4 from the two volumes and ...
*April 5, 2007 by Christine*

**chemistry-lattice energy**

Determine the lattice energy for CaBr2 if the enthalpy of solution for CaBr2 is -145 kJ/mol, and the heats of hydration for Ca2+ and Br- are -1650 kJ/mol and -292 kJ/mol respectively.
*October 1, 2012 by Bru*

**physics**

A stone is projected upward at an angle of 60degree to the horizontal from the top of a tower of height 100meter and it hits the ground at a point. If the initial velocity of projection is 100meter. Calculate the maximum height of the stone above the ground. Calculate the time...
*January 3, 2012 by John*

**physics**

A stone is projected upward at an angle of 60degree to the horizontal from the top of a tower of height 100meter and it hits the ground at a point. If the initial velocity of projection is 100meter. Calculate the maximum height of the stone above the ground. Calculate the time...
*January 3, 2012 by John*