# Heat Of Formation & Gas Laws

Please solve and show all calculations.

1.

An ideal gas at 300K and 2.00 atm pressure in a 400 cm^3 container has its pressure increased to 5.00 atm and its volume increased to 6000 cm^3. What is the final temperature?

2.

The vapor pressure of water at 23 degrees celcius is 21.07 torr. Find the vapor pressure at 23 degrees celcius of the solution formed by dissolving 15.0 g o C6H12O6 (a nonvolatile solid) in 72.0 g of H2O.

3.

The specific heat of ice is 2.09 Jg-K and the specific heat of liquid water is 4.18 J/g-K. The heat of fusion of ice is 6.01 kj/mol. Find the heat needed to convert 36.0 g of ice at -10 degrees celcius to liquid water at 20 degrees celcius.

4.

The freezing point of C6H6 is 5.50 degrees celcius and Kf = 5.12 degrees celcius (mol/kg) for C6H6. A solution of 6.42 g of the nonelectrolyte compound X in 183.2 g of C6H6 freezes at 4.00 degrees celcius Find the molecular weight of X.

https://brainmass.com/chemistry/gas-laws/heat-of-formation-gas-laws-538113

#### Solution Preview

1. P1V1 / T1 = P2V2 /T2

T2 = P2V2T1 / P1V1 = 5 x 6000 x 300 / (2 x 400) = 11250 K

2. Vapor pressure of solution = mole fraction of solvent x pure vapor pressure of solvent

Moles of solvent = 72 / 18 = 4 ...

#### Solution Summary

Four problems based on gas laws, vapor pressure, heat of formation and molality are solved.

Gas Laws & Heat Of Reaction

1.

For the reaction

2 NO(g) + O2(g) -->2 NO2(g)

deltaH = -126.0 kJ at 25C.

(a) Calculate the amount of heat transferred when 333 g of NO(g) reacts with O2(g) at 25C and 1 atm.

(b) Does this heat flow into the system or does it flow to the surroundings?

(c) Is this reaction exothermic or endothermic?

2.

If 8675 J of heat flows into 135.0 g of water initially at 20.0C, find the final temperature of

the water. The specific heat of water is 4.18 J g^-1 K^-1.

3.

Find the molecular weight of a gas if 22.24 g of the gas in a 7045 cm^3

container at 20°C exerts a pressure of 698 torr.

CONSTANTS

R = 0.08206 L atm mol^-1 K^-1

1 atm = 760 torr

c = 3.00 x 10^8 m/s

h = 6.63 x 10^-34 J . s

4.

Calculate deltaH at 25C is -1790 kJ for the reaction

C3H6O(l) + 4O2(g) -->3 CO2(g) + 3 H2O(l)

Given these f deltaH values at 25C: -394 kJ/mol for CO2(g), -286 kJ/mol for H2O(l), and 0 for

O2(g), find f deltaH for C3H6O(l).

5.

What volume of H2(g) at 27C and 1.08 atm is produced when

45.3 g of Al reacts as follows:

2Al + 6HNO3(aq) --> 2Al(NO3)3 + 3H2

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