Friday

January 30, 2015

January 30, 2015

Number of results: 19,527

**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*

**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*

**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*

**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**

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 - 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**

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*

**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*

**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*

**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*

**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 - 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*

**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 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**

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*

**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 -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*

**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*

**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*

**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*

**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*

**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*

**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 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*

**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*

**chemistry**

How do you calculate the theoretical cell voltage? 1) Zn|Zn^+2 (1M)| Cu|Cu^+2 (1M) 2) Cu|Cu^+2 (1M)| Zn|Zn^+2 (1M) 3) Fe|Fe^+2 (1M)| Cu|Cu^+2 (1M) 4) Zn|Zn^+2 (1M)| Cu|Cu^+2 (0.1M) 5) Cu|Cu^+2 (1M)| Cu|Cu^+2 (0.1 M) Now 4 and 5 have different moles how do you calculate those ...
*July 19, 2012 by fenerbahce *

**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*

**Math**

An airplane is heading due south at a speed of 590km/h. If a wind begins blowing from the southwest at a speed of 65.0km/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 12, 2009 by Anne*

**Physics**

A worker applies a constant force of magnitude F = 339 N on a crate in a direction è = 26.1o above the horizontal as he pulls it across a level floor through a distance of s = 7.20 m. The mass of the crate is m = 53 kg and the coefficient of kinetic friction between the floor ...
*December 18, 2012 by Sara H*

**chem**

a buffer is made by adding 150 ml of .595M BaF2 and 0f .500M of HF solution. calculate the pH of this buffer system calculate the pH of this buffer after adding .100 mol Hcl calculate the pH of this buffer after adding .0750 mol Ca(OH)2 ka(HF)= 6.9x10^-4 kb(F-)= 1.4 x 10^-11
*March 1, 2010 by simi*

**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*

**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*

**Chemistry**

A total of 2.00 mol of a compound is allowed to react in a foam coffee cup that contains 141 g of water. The reaction caused the temperature of the water to rise from 21.0 to 24.7 degrees Celsius. What is the enthalpy of this reaction? Assume that no heat is lost to the ...
*October 11, 2010 by Karen*

**physics**

A 5.20 package slides 1.57 down a long ramp that is inclined at 13.0 below the horizontal. The coefficient of kinetic friction between the package and the ramp is = 0.305 Calculate the work done on the package by friction. Calculate the work done on the package by gravity. ...
*October 4, 2012 by Matt*

**physics**

A 5.20 package slides 1.57 down a long ramp that is inclined at 13.0 below the horizontal. The coefficient of kinetic friction between the package and the ramp is = 0.305 Calculate the work done on the package by friction. Calculate the work done on the package by gravity. ...
*October 5, 2012 by Matt*

**chem please help drbob222**

What will be the result of a reaction if its enthalpy change is positive, its entropy change is negative and Gibbs free energy is positive? A. Spontaneous, if the temperature is high B. Nonspontaneous, if the temperature is low C. Always spontaneous D. Never spontaneous
*November 26, 2014 by Morgan *

**Chemistry**

I need help on how to calculate the following please: Calculate the risk assesment of the amount of the ozone in the air between the hours of 4pm and 6pm where I live(Corpus Christi,Texas)
*August 27, 2011 by Jelly*

**Physics**

NEED HELP On a flat battle ground, a catapult is used to launch a rock with a velocity of 25m/s at angle 30 degrees above the horizontal.? Sketch the situation and decompose the initial velocity vector. WHat are the initial values for Vx and Vy? Calculate the maximum height ...
*August 19, 2014 by Jeesha*

**Physics**

The following figure represents the ride for a cart with a mass of 200 kg along a frictionless track. a. Calculate the velocity of the cart at points A, B, and C if the cart is dropped from a height of 100m with a initial velocity of 10 m/s. b. Calculate the height of the ...
*July 25, 2014 by Liz*

**Chemistry**

Mass (before reaction): test tube + HCl(aq) + stir bar + capsule 26.600 g Mass (after reaction): test tube + HCl(aq) + stir bar + capsule 25.300 g Volume of water displaced from the squirt bottle 148 mL Temperature of the CO2(g) 287.4 K Pressure (atm) 1.032 atm Using this data...
*October 21, 2012 by Karina*

**chemistry**

A. Strong Base 1.) What is the concentration of a solution of KOH for which the pH is 11.89? 2.) What is the pH of a 0.011M solution of Ca(OH)2? B. Weak Acid 1.) The pH of a 0.060M weak monoprotic acid HA is 3.44. Calculate the Ka of the acid. 2.) The pH of 0.100M solution of ...
*January 20, 2011 by jaycab*

**chemistry**

Which of the following equations represents a reaction for which the delta H can be called a standard enthalpy of formation, delta Hf? a) FeO(s) + CO2(g) -> FeCO3(s) b) 1/2 N2(g) + 2 O(g) -> NO2(g) c) 2 Na(s) + Cl2(g) -> 2 NaCl(s) d) Ba(s) + N2(g) + 3 O2(g) -> Ba(...
*January 23, 2012 by timmy*

**Chemistry**

Given the following hypothetical equations, 2A + B → 3C + 2D ΔH = -46.7kJ C → B ΔH = 13.1kJ 2E → B ΔH = 84.5kJ, what is the enthalpy change (kJ) for the following reaction? A → D + 2E
*March 7, 2012 by John*

**Chemistry **

Why wouldn't you do this reaction directly in a lab (and would rather use Hess' Law to determine the enthalpy of formation)?: 1/2N2(g) + 2H2(g)+ 1/2Cl2(g) -> NH4Cl(s) I don't think the reactants are that dangerous...? It's still pretty safe to do in a lab, isn't it? Are ...
*February 18, 2013 by a Canadian*

**Physics**

A stone that starts at rest is in free fall for 8.0 s. a.Calculate the stone's velocity after 8.0 s. b. What is the stone's displacement during this time? Given: t = 8.0 s a = 9.81 m/s^2 For a, in order to calculate the velocity, should i use d = vit + 1/2 at^2 and only use ...
*December 25, 2009 by Priscilla*

**chemistry**

the enthalpy of fusion of ice is 6.02 kJ/mol. the heat capacity of liquid water is 75.4 J/molC. What is the smallest number of ice cubes at 0 degrees C each containing one mole of water, necessary to cool 500g of liquid water initially at 20.0 degree C to 0.0 degree C
*May 24, 2011 by el*

**Maths**

The distance from TDC (top dead centre) for the pin is given by x when the crank is at angle . Hence : i) Give an equation for x in terms of the other variables (r, L and ). ii) If the crank rod is rotating at a constant value of ω calculate the speed of ...
*May 17, 2011 by Karl Haxell*

**math**

The distance from TDC (top dead centre) for the pin is given by x when the crank is at angle . Hence : i) Give an equation for x in terms of the other variables (r, L and ). ii) If the crank rod is rotating at a constant value of ω calculate the speed of ...
*May 17, 2011 by Karl Haxell*

**Maths**

In an orthonormal system, you're given the following: Point P(1,2) Lina a=cartesian eqn:4x-3y+6=0 Line b=parametric eqns:x=-5+3& y=-& (real n°) Circle z=cartesian eqn:x²+y²-2x-3=0 (a)Calculate the angle between lines a an b (b)Calculate the coordinates of the point of ...
*May 4, 2008 by Anonymous*

**Mathematics**

In an orthonormal system, you're given the following: Point P(1,2) Lina a=cartesian eqn:4x-3y+6=0 Line b=parametric eqns:x=-5+3& y=-& (real n°) Circle z=cartesian eqn:x²+y²-2x-3=0 (a)Calculate the angle between lines a an b (b)Calculate the coordinates of the point of ...
*May 18, 2008 by Anonymous*

**chemistry**

1998 scientists using a special type of electron microscope were able to measure the force needed to break a single chemical bond. If 2.0 x 10^-9 N was needed to break a C-Si bond, estimate the bond enthalpy in kJ/mol. Assume that the bond had to be stretched by a distance of ...
*September 26, 2011 by Amber*

**Math**

If a = 3i + 2j - k and b = -2i + j calculate each magnitude. a) a + b I got sqrt3, but the answer at the back of the book says sqrt11. 2) If D(3,4,5) and E(-2,1,5) are points in space calculate each expression and state what it represents. |OD| can you please do those and ...
*March 29, 2008 by Anonymous*

**Chemistry**

What is the enthalpy change (in kJ) for burning 49.0 g of methyl alcohol? I tried this question and got the wrong answer of 1047.74. 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...
*October 19, 2012 by Anonymous*

**college chemistry**

Use the thermochemical equations shown below to determine the enthalpy (kJ) for the reaction: H2SO3(l)=>H2S(g) + 3/2O2(g) H2SO3(l)=>H2O(l) +SO2(g) DH=62KJ SO2(g)=>S(s) + O2(g) DH=297KJ H2S(g) + 1/2O2(g)=>S(s) + H2O(l) DH=-155KJ
*October 24, 2010 by sara*

**Chemistry**

A 5.0-g Sample of KBr at 25.0 degrees celsius dissolves in 25.0 degrees celsius 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?
*December 2, 2010 by Sally*

**Chemistry**

The enthalpy of vaporization of chloroform (CHCl3) is 29.2 kJ mol-1 at its normal boiling point 61.2 Celsius. what is the standard change in entropy for vaporization of chloroform at its normal boiling point? Answer I got was 29.2/334.2 = 0.0873. (CORRECT?)
*April 2, 2013 by Viv*

**chemistry**

how in the world do you do this problem? Use the thermochemical equations shown below to determine the enthalpy (kJ) for the reaction: H2SO3(l)=>H2S(g) + 3/2O2(g) H2SO3(l)=>H2O(l) +SO2(g) DH=62KJ SO2(g)=>S(s) + O2(g) DH=297KJ H2S(g) +1/2O2(g)=>S(s) + H2O(l) DH=-...
*October 24, 2010 by anonymous*

**chemistry - energy and change rev (help)**

the below 2questions i could not answer while revising for this chapter pls help me out a little. 58. When a vehicle is parked in the sunlight on a hot summer day, the temperature inside can approach 55°C. One company has patented a non-CFC propelled aerosol that can be ...
*March 23, 2011 by Babelii*

**chemistry**

For a particular isomer of C8H18, the following reaction produces 5113.3 kJ of heat per mole of C8H18(g) consumed, under standard conditions. C8H18(g) + 25/2(O2)(g) -> 8CO2(g) + 9H2O(g) DeltaH= -5113.3 kJ What is the standard enthalpy of formation of this isomer of C8H18(g)?
*January 29, 2012 by Mike*

**chemistry**

calculate [h3o] in solutions. 0.040 of HCl and 0.080 HOCl. 2. calculate OH for the solutions of 0.0063 ba (OH)2 and 0.0110 of BaCl2
*April 11, 2010 by anonymous*

**math**

Consider the function defined below. y = 2t3 - 4t2 + 3 (a) Calculate the second derivative. y '' = (b) Calculate the third derivative. y ''' =
*June 21, 2010 by Jack*

**Chemistry**

Calculate how much heat 32.0 g of water absorbs when it is heated from 26.0°C to 73.5°C. In joules, and then we have to calculate calories too, how is that done? I was absent. Thanks so much!
*May 25, 2011 by Jane*

**Chemistry **

Calculate the wavelength of broadcast waves. Calculate the energy associated with the broadcast frequency for WPHT, 1210 kHz.
*November 5, 2011 by Anonymous*

**math**

calculate the mass (in SI units) of a 150ib human being? m= Calculate the weight ( in English units) of a 200kg rhino m=
*January 26, 2012 by bree*

**epidemiology**

In a fictitious study, 100 out of 1000 people aged 60 years and over were positive in detecting breast cancer using Tumour Biopsy (gold standard). Using mammography, 90 of breast cancer patients and 135 healthy persons were also positive by this test. (I) Calculate and ...
*August 18, 2012 by Ekrem*

**Chemistry**

When 23.6 of calcium chloirde CaCl2 was dissolved in water in a calorimeter, the temperature rose from 25.0 degrees C to 21.56 degrees C. If the heat capacity of the solution and the calorimeter is 1071 J/ degrees C, what is the enthalpy change when 1 mol of sodium nitrate ...
*November 1, 2007 by Lauren*

**chemistry**

When water freezes, the phase change that occurs is exothermic (DH = -6.02 kJ). Based on the change in enthalpy, you would expect that water would always freeze. Use the concepts of entropy and free energy to explain why this phase change is favourable only below o degrees ...
*April 6, 2008 by Sarah*

**Chemistry**

For ethanol, C2H5OH, which is mixed with gasoline to make the fuel gasohol, H°f = -277.63 kJ/mol. Based upon data in Table 6.2, and that the density of ethanol is 0.787 g•cm-3, the number of kilojoules released by burning completely 2.40 gallons of ethanol is ? *Table 6.2 ...
*October 16, 2011 by A*

**ap chem**

A 9.00 M solution of a weak acid, HA, has a pH of 1.30 1.) calculate [A-] at equilibrium 2.) calculate [HA] at equilibrium Use pH to get (H^+). Ka = (H^+)(A^-)/(HA) (A^-) = (H^+). (HA) = 9 Plug and chug. Post your work if you get stuck.
*March 22, 2007 by Jaron*

**Physics**

A particle's initial velocity is given by vox = -1.0 m/s and voy = 3.0 m/s. Its acceleration is ax = 0.50 m/s^2 and ay = -0.90 m/s^2 (a) Calculate its velocity 2.0 s later. (b) Calculate its displacement at that time.
*October 4, 2009 by Sandhu*

**statistics**

GIVEN THE FOLLOWING STATISTICAL VARIABLES A:m(A)=5 B:m(B)=13 var(A)=25 Var(B)=6 1.calculate mean of Z= 4B-2A 2.Calculate the Standard Deviation assuming cov (A,B)=0
*August 17, 2010 by RASHMI*

**physics**

A force of 303.0 N is used to push a 160 kg mass 30.0 m horizontally in 3.00 s. (a) Calculate the work done on the mass. 1 kJ (b) Calculate the power developed. 2 kW
*December 12, 2011 by Anonymous*

**chemistry**

calculate r.m.s velocity of he molecule at 300k.also calculate the total k.e(in calories)of the molecules in one litre he at 300k & 1atm?
*July 6, 2012 by dip*

**Math calculate depreciation**

please explian how to calculate depreciation for federal income taxes what method do I use thanks :)
*November 14, 2007 by Anonymous*

**calculus**

calculate the indefinite integral 2sec^2x dx (cosx)/(sin^3x) dx calculate the definite integral interval pi/4, pi/12 csc2xcot2x dx
*January 6, 2008 by anonymous*

**geometry**

In the following figure given a circle C(o,3) Bp=AB and BA^N = 30 a) Calculate AP,BN and AN b)Calculate AQ and BQ c) Show That M is the mid point of (AP) d)Show that (OM)is perpendicular to (A)
*April 16, 2010 by Nour *

**physics **

A spherical conductor has a radius of 14.0 cm and charge of 26.0 µC. Calculate the electric field and the electric potential (a) r = 10.0 cm, (b) r = 20.0 cm, and (c) r = 14.0 cm from the center. how do i calculate k?
*February 7, 2012 by confused*

**Chemistry-Help**

An AM radio station broadcasts at 1060 kHz. Calculate the wavelength of the corresponding radio waves. How do I calculate this?
*April 30, 2012 by Liz*

**Physics**

An electric dipole comprised of two charges Q and -Q are separated by a distance of 3.0 cm. Assume Q = 2.0x10^-6 C and -Q = -2.0x10^-6 C. Find the magnitude and direction of the electric field vector E and point P, which is 4.0 cm to the right of the center of -Q. Find the ...
*March 13, 2012 by Michelle*

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