Thermochemistry Q2

A substance with a high specific heat:

• Is always extremely hot.
• Requires a lot of energy to become hot.
• Is not heavy.
• Does not requires a lot of energy to become hot.

Refer the the following question:
2N₂ + 3H₂ --> 2NH₃ + 46 kJ
How much energy would be produced if only 1 mol of nitrogen was reacted?

• 92 kJ
• 0.143 kJ
• 23 kJ
• 15 kJ

The specific heat of liquid bromine is 0.2 J/gK. How much heat is required to raise the temperature of 100. grams of bromine from 15 K to 25 K?

• 30 J

• 500 J

• 20 J

• 200 J

How much heat is released when 36 grams of water is frozen at 0 C? The heat of solidification is 6.02 kJ/mol.

• 18 kJ

• 220 kJ

• 12 kJ

• 2 kJ

Some average bond enthalpies, in kJ/mol, are as follows:
H-H = 436
Cl-Cl = 242
H-Cl = 431
What is the enthalpy change for the decomposition of hydrogen chloride?
2 HCl --> H₂ + Cl₂

• -184 kJ
• + 184 kJ
• - 247 kJ
• + 247 kJ

The enthalpy change for the reaction
C(s, graphite) + 1⁄2O₂(g) --> CO(g) cannot be measured directly since some carbon dioxide is always formed in the reaction.
It can be calculated using Hess’s Law and the enthalpy changes of combustion of graphite and of carbon monoxide.
C(s, graphite) + O₂(g) --> CO₂    ΔH=-394 kJmol^–1
CO(g) + 1⁄2O₂(g) --> CO₂  ΔH=-283 kJmol^–1  
The enthalpy change for the reaction of graphite with oxygen to give carbon monoxide is 

• -677 kJmol^–1 
• +111 kJmol^–1 
• -111 kJmol^–1 
• +677 kJmol^–1 

The standard enthalpy changes of combustion of carbon, hydrogen and methane are shown in the table. 
Which one of the following expressions gives the correct value for the standard enthalpy change of formation of methane in kJ mol^–1?
C(s) + 2H₂(g) → CH₄(g) 

• 394 + (2 × 286) – 891 
• –394 – (2 × 286) + 891 
• 394 + 286 – 891 
• –394 – 286 + 891 

During the vaporization of water, the kinetic energy...

• increases, while potential energy decreases
• increases, while potential energy stays the same
• stays the same, while potential energy increases
• stays the same, while potential energy decreases

Which 1 g sample will have the highest temperature after the addition of 200 J of energy?

• H₂O(l)

• H₂O(g)

• Cu

• Pb

If 5.00 grams of water is cooled from 65.2 °C to 35.6 °C, what is the heat change?

• 619 J
• -619 J
• 148 J
• -148 J