Question

1. A reaction takes place in 100.0 ml of solution.  The solution increases in temperature by 10.0 ^oC. Assuming the specific heat of the solution is the same as water and the density of the solution is 1.000 g/ml, how much heat energy was emitted by the reaction?

a. -4.18 kJ

b. 4.18 J

c. -4.18 J

d. +4.18 kJ

2. Some solid NH4NO3 is dissolved in water that starts at room temperature. When you touch the beaker after the solid is dissolved, it is now lower temperature than room temperature. (The beaker feels cold). Which statement is true?
      
a. The process of dissolving ammonium nitrate in solution is exothermic
      
b. The process of dissolving ammonium nitrate in solution is neither exo or endothermic
      
c. The process of dissolving ammonium nitrate in solution is endothermic

3. Given this reaction and its enthalpy change
C (gr) + O2 (g) --> CO2 (g) ∆Hrxn = -393.5 kJ
What is the reaction that has an enthalpy change of
∆Hrxn = +393.5 kJ?
      
a. CO2 (g) -> C (gr) + O2 (g)
      
b. 2CO2 (g) -> 2C (gr) + 2O2 (g)
      
c. ½ C (gr) + ½ O2 (g) -> ½ CO2 (g)
      
d. C (gr) + O2 (g) -> CO2 (g)

Answer 1

1.

Volume of the solution = 100.0 mL

Density = 1.00g / mL

Hence, mass of the solution is

The change in temperature is positive as the temperature of the solution is increasing.

the heat capacity of the solution is

Assuming all the heat released by the reaction is absorbed by the solution

Hence, the correct choice is option d) +4.18 kJ

2.

Since the temperature of the beaker has decreased from room temperature, the process of dissolution has taken heat from the surrounding. Which means the dissolution process of is endothermic.

hence, the correct option is C) The process of dissolving ammonium nitrate in solution is endothermic.

3.

Enthalpy change for the reaction below is -393.5 kJ

If enthalpy change is negative, it means it is an exothermic reaction.

Hence, the above reaction produces 393.5 kJ of energy.

If the enthalpy change is positive, it means the reaction requires that amount of energy.

Also If reaction releases energy, its reverse reaction will happen if I provide that amount of energy to the products.

Hence, for the reverse reaction the value of enthalpy change results in a change of sign.

Hnce, the reaction with enthalpy change of +393.5 kJ is

Hence, the correct choice is a)