Wednesday

November 25, 2015
Number of results: 21,595

**Chemistry**

3. A liquid hydrocarbon (Cx Hy) is found to be 16.37% H by mass. A 1.158-g vaporized sample of the hydrocarbon has a 358 mL volume at 71.0 C and 749 mmHg. what is the molecular formula for this hydrocarbon? 4. A 1.00 g Sample of C7H603 (s), us completely burned in a bomb ...
*June 21, 2011 by Katrina*

**AP Chemistry**

Ammonia, NH3, is used as a refrigerant. At its boiling point of -33 degress Celcius, the enthalpy of vaporization of ammonia is 23.3 kJ/mol. How much heat is required to vaporize 355 g of ammonia at -33 degrees Celcius? a. 1.12 kJ b. 152 kJ c. 251 kJ d. 486 kJ e. 8.27 x 10^3 kJ
*April 4, 2008 by Joe*

**Chemistry 152**

For a certain reaction, the enthalpy change is -148.5 kJ, the entropy change is 256 J/K, and the free energy change is -250.1 kJ. At what temperature is the reaction occurring, in C? Choose one answer. a. 85 b. 102 c. 124 d. 158 e. 210
*July 3, 2010 by Car*

**chemistry 104**

estimate the enthalpy change for each of the following reaction: a) H2C=O(g)+HCl(g .....> H3C-O-Cl(g) b)H2O2(g)+2CO(g).....> H2(g)+2CO2(g) c)3H2C=CH2(g).....> C6H12(g) (the six carbon atoms form a six-membered ring with two H atoms on each C atom)
*November 16, 2012 by oluchi*

**chemistry**

How many liters of hydrogen gas are produced during an enthalpy change of -50kJ, assuming STP conditions? 1L= 1kg zn+ hno3 yields znn03 + 1/2 h2 +100kJ -50 kj x (1mol h2/ 100kj) X (2.02g / 1 mol) h2 ) = 1.01 g please help tried to get the answer but it it supposed to be 11.02 ...
*September 21, 2015 by mariam*

**Chemistry**

I don't really know how to go about this, Please help 1. Calculate the number of moles of the gas. Calculate the volume the gas would occupy at 100.0 C and 15.0 atm. 10.8 g He 2. Given the volume of 54.0 C and 790 torr, calculate the number of moles and mass. 38.1 L CO
*March 11, 2013 by Geoffrey*

**Chemistry**

2M +6HCl–>2MCl+3H2 Delta H= -638.0 Kj HClg—>HCl aq= Delta H -74.8 Kj H2+Cl2–>2HCl Delta H -1845.0 Kj MCl3s–> MCl3 aq Delta H -249.0 Kj Use the information above to determine the enthalpy of the following reaction. 2M +3Cl2–>2MCl3 Delta H =???
*March 22, 2013 by Raul*

**physics please help **

A rock of mass 5kg is pushed over the edge of a cliff which is 200m high 1.ignore air resistance and calculate the speed of the rock at the bottom of the cliff. In reality air resistance cannot be ignored. The rock eventually reaches terminal velocity of 30m/s 2.calculate the ...
*April 16, 2015 by Annah van tonder*

**Chemistry **

when potassium in water are combined they produced 4000.0 kJ of heat along with potassium hydroxide and hydrogen gas. how much energy would be produced if you dumped a 1.00 kg chunk of potassium into a swimming pool? s this reaction what is the enthalpy change?
*October 19, 2015 by Al*

**physics**

a ball is thrown straight up with a speed of 8.0 m/s from a third-floor window located 13.0 m above ground. Calculate the maximum height, measured from the ground, of the ball; calculate the ball's velocity when it reaches the ground, and calculate the total time it takes the ...
*October 13, 2014 by Arleen *

**Physics**

2. Charge q1 is located at (0,+30 cm). Charge q2 is located at (0, -30 cm) q1 = +25 pC q2= -75 pC A) Calculate the potential energy of the charges B) Calculate V1, the electric potential at the orgin due to charge q1, and V2, the electric potential at the orgin due to charge ...
*April 12, 2011 by YoungTangerine*

**Chemistry**

Calculate whether or not a precipitate will form if 1.30 mL of 0.80 M NH3 are added to 2.2 L of 1.0 10-3 M FeSO4. Calculate Q.
*March 16, 2012 by Tanya*

**chemistry**

How do I calculate the freezing point of 11.3g FeCl3 in 155g water? I know how to calculate i and m but how do you find Kf?
*December 4, 2012 by Farah Massardi*

**algebra functions**

how do i calculate this if f(x)= 3x+1 and g(x)=x+2 find (fg)(x)and calculate (fg)(2) is this multiplication and if so what do i do first any help would be appreciated
*October 20, 2013 by christin*

**chemistry**

calculate the change in pH when 5 ml of 0.01M HNO3 is added to 50 ml of water. I know how to calculate pH, but not when it is changing.
*April 1, 2015 by Yvonne*

**geometry**

sorry about nos. A(-3, 2) B (5, -4).calculate midpoint. Calculate length of AB, AM, and MB. Thanks again
*April 6, 2015 by robin*

**Math**

The function g and h are defined by g(x) 4x+1/3x-2 and h(x)5x-2 Calculate g(0) 4(0)+1/3(0)-2 = -1/2 Calculate h(1/5) 5(1/5)-2 = -1 Determine the value of gh(1/5) 4(5(1/5)-2) (3(1/5)-2)= 4(-1/-1.4)= 2.85 is this right??
*September 9, 2009 by Keisha*

**Chemistry**

Calculate the weight percent of water in NiSO4 6H2O, how to calculate it?
*December 8, 2010 by Brittany*

**Chemistry**

Calculate the weight percent of water in NiSO4 6H2O, how to calculate it?
*December 8, 2010 by Brittany*

**Chemistry**

Calculate the weight percent of water in NiSO4 6H2O, how to calculate it?
*December 8, 2010 by Brittany*

**chemistry**

for a .001M solution of methionine: a) calculate the isoelectric pH b) calculate the isoionic pH
*April 7, 2013 by Lana*

**Chemistry**

For a solution that is 0.20 M HCN(aq) with a Ka=4.9x10^-10 a. calculate the [H+] b. calculate the [OH-] c. what's the pH? Please show your work on how to solve it. Thank you
*January 27, 2011 by Sharon*

**Grade 12 Advanced Functions**

One zero of f(x)=x^3+4x^2+x+c is -3. a) calculate the value of c. b)calculate the other zeros.
*October 13, 2011 by Rebecca*

**algebra functions**

how do i calculate this if f(x)= 3x+1 and g(x)=x+2 find (f+g)(x) and calculate (f+g)(1) a little confused can some one please help me thank you
*October 20, 2013 by christin*

**chemistry**

Calculate the freezing point of a water solution at each concentration. 1.40m? What are the steps to calculate this?
*November 19, 2014 by Luis*

**chemistry**

The enthalpy of combustion of benzoic acid,C6H5COOH, which is often used to calibrate calorimeters, is -3227kJ/mol. When 1.236g of benzoic acid was burned in a calorimeter, the tempurature increased by 2.345K. What is the specific heat of the calorimeter?
*November 2, 2008 by annemarie*

**chem**

The normal boiling point of water is 100.00 degrees celsius and the enthalpy of vaporization at this temperature is 40.657kj/mol. What would be the boiling point of water if it were based on a pressure of 1 bar instead of the standard atm?
*November 18, 2008 by tomi*

**Science**

A boy exerts a force of 15N to push a motor bike which has flat tyre for a distance at 30m.calculate the mass of the motor bike. Calculate the density of the motor bike.calculate the work done by the boy.[take g=10m|sm2
*May 14, 2012 by Nicholas*

**Science**

A boy exerts a force of 15N to push a motor bike which has flat tyre for a distance at 30m.calculate the mass of the motor bike. Calculate the density of the motor bike.calculate the work done by the boy.[take g=10m|sm2
*May 14, 2012 by Nicholas*

**Chemistry**

The molar enthalpies of combustion of CH3COCOOH(l)CH3COOH(l) and CO(g) are respectively -1275kJ/mol, -875kJ/mol, and -283kJ/mol. What is the enthalpy change for the reaction below? CH3COCOOH= CH3COOH+CO a)1867kJ b)-1867kJ c)117kJ d)-117kJ e)-2433kJ I think it's d) Consider the...
*July 24, 2010 by Bobby*

**Chemistry**

Dioxane C4H8O2 has an enthalpy of fusion = 145.8 Jg-1 and its melting point temp is 11 degrees C. How much energy is required to transform 142g of solid dioxane at 11 degrees C into liquid dioxane, also at 11 degrees C?
*February 1, 2009 by Amanda*

**physics**

Rotating blade (body force in axial loading) blade is fixed to a rigid rotor of radius R spinning at ω rad/sec around the vertical z-axis. Neglect the effects of gravity. Calculate the peak stress in the blade: σmaxn Calculate the blade elongation: δ Calculate ...
*May 3, 2013 by rka*

**science please help and explain asap**

A rock of mass 5kg is pushed over the edge of a cliff which is 200m high 1.ignore air resistance and calculate the speed of the rock at the bottom of the cliff. In reality air resistance cannot be ignored. The rock eventually reaches terminal velocity of 30m/s 2.calculate the ...
*April 15, 2015 by Annah van tonder*

**chemistry**

how do i calculate the [OH-] and [Ca2+] using the equivalence point? Then I have to calculate the Ksp for calcium hydroxide.
*November 1, 2011 by Kris*

**Chemistry **

Calculate the molarity of the H3PO4 solution?This the question Answer has to be: MH3PO4 = ? mol/L but I don't know how to calculate it. Thanks for help so far
*October 26, 2014 by Duke*

**Fractions**

Calculate the Following 2/3 + 1/6 + 1/6= I caluclated 2/3 x 2/2 = 4/6 So you would calculate 4/6 + 1/6 + 1/6= 6/6 which = 1 Is that correct
*July 24, 2008 by Jennyv*

**Chemistry**

Hi! I was studying for an exam (lol) and I came across something I don't quite understand.. could someone help me with Standard Enthalpy of Formation? The equation in my notes looks like this: ΔHºrxn = ΣΔHºf(products) - ΣΔHºf(reactants) Thanks in advance!
*December 14, 2008 by Chris*

**chem**

The complete combustion of butane, (g) is represented by the equation C4H10+13/2O2->4CO2+5H20 STANDARD ENTHALPY IS -2877KJ/MOL How much heat, in kilojoules, is evolved in the complete combustion of 12.8L C4H10 at 23.8degrees celsius and 744mmhg ?
*October 8, 2008 by tomi*

**college chemistry**

The enthalpy of combustion of benzoic acid,C6H5COOH, which is often used to calibrate calorimeters, is -3227kJ/mol. When 1.236g of benzoic acid was burned in a calorimeter, the tempurature increased by 2.345K. What is the specific heat of the calorimeter?
*November 3, 2008 by annemarie*

**chemistry**

a 3.35g sample of solid silver reacted in excess chlorine gass to give a 4.45g sample of pure solid AgCl. the heat given off was 3.95kJ at constant pressure. what is th enthalpy of formation of AgCl?
*June 21, 2010 by Ellie*

**chemestry**

the enthalpy of combustion of benzoic acid C6H5COOH, which is used to calibrate calorimeters usualmete is -3227 kJ mol-1. burning 1.453g of benzoic acid into a calorimeter, the 2,265 ° C temperature increase what is the heat capacity of the calorimeter?
*April 23, 2015 by Daniela*

**College Chemistry**

The density of a 0.0122 M KMnO4 is 1.037 g/mL. Suppose 26.35 g of 0.0122 M KMnO4 are required to titrate 1.072 g of a household H2O2 solution. a)Calculate the mL of MnO4^- added to reach the endpoint. b)Calculate the moles of MnO4^- added to reach the endpoint. c)Calculate the...
*February 25, 2014 by Kelsey*

**Chemistry**

In a bomb calorimeter, a 6.50 g sample of octane (C8H18) is combusted. The combustion enthalpy for octane is -5.45 MJ per mol C8H18. The temperature change of the calorimeter is 16.5 oC. What is the heat capacity of the calorimeter?
*March 14, 2014 by Mary*

**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**

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*

**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*

**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*

**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*

**Chemistry**

You mix 45 ml of .20M HCl with 45 ml of .20M KOH in a calorimeter. The temperature of both reactions before mixing is 21.5oC. The temperature rises for the mixture to 22.7oC after mixing. What is the enthalpy change per mole of water produced?
*July 22, 2015 by Jessica*

**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*

**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*

**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*

**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*

**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*

**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*

**chemistry**

10mL of 0.500M HCl was added to 50mL of 0.100M NaOH in a coffee cup calorimeter, and the temperature increased from 22.3°C to 23.1°C. What is the experimentally determined enthalpy of neutralization of HCl (in kJ/mol)? The specific heat of water is 4.184J/g•°C, and the heat ...
*October 19, 2015 by Lay*

**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*

**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*

**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*

**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*

**physical science(elecrostatics)**

A(-9x10^-9 C) 20mm B(5x10^-9 C) (a)calculate the force between the charges (b)if A comes in contact with B Calculate the new charge on A and B
*September 16, 2015 by jonathan*

**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*

**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*

**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*

**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**

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*

**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**

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 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*