Question

Thermochemistry - Prelab Name: 1. Classify each of the following transformations as exothermic or endothermic (a) Combustion of natural gas (CH): (b) Sublimation of solid CO2: (c) Freezing of H2O in a pond: 2. An exothermic reaction occurs within a solution in a calorimeter. Which of the following statements is correct? (Circle your choice) 4ren > while son < 0 Gren > O while soin > 0 Arun Arun while son > soin < 0 while 3. A 5.0 g block of aluminum at 30.°C is heated to 90. °C. If the heat capacity of Al is 0.900 1/8°C, calculate the heat (q) required to warm the aluminum. 4. The 5.0 block of aluminum at 90. °C is placed in 150. g of H2O (C= 4.184 J/e°C) held at a temperature of 25 °C. What is the temperature of the mixture when thermal equilibrium is established?

Answer 1

1)

A) Combustion of any gas is always exothermic whether it is any gas gas or hydrocarbon.

B) Sublimation is endothermic.

C) Freezing is exothermic.

2)

For exothermic reaction;

Q(rxn) < 0

Q(sol) < 0

3)

Q = m * s * Delta T

Q = 5 * 0.900 * (90-30)

Q = 270 J ...Answer

4)

Q ( aluminum) = Q (water)

5 * 0.900 * (90 - T) = 150 * 4.184 * (T - 25)

405 - 4.5T = 627.6T - 15690

T = 25.46° C .....Answer

Let me know if any doubts/answer is not matching.