# Thermochemistry (Worksheet)

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Section: _____________________________

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Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

## Q1

A 295 g aluminum engine part at an initial temperature of 3.00°C absorbs 85.0 kJ of heat. What is the final temperature of the part? ( c of Al = 2.42 J/g * K)

## Q2

A 27.7 g sample of ethylene glycol loses 688 J of heat. What was the initial temperature of the ethylene glycol if the final temperature is 32.5°C ( c of ethylene glycol = 2.42 J/g *K)

## Q3

When 165 mL of water at 22°C is mixed with 85mL of water at 82°C, what is the final temperature? (assume d of water = 1.00 g/mL)

## Q4

An unknown volume of water at 18.2°C is added to 24.4 mL of water at 35.0°C. If the final temperature is 23.5°C, what was the unknown volume? (assume d of water = 1.00 g/mL)

## Q5

A 505 g piece of copper tubing is heated to 99.9°C and placed in an insulated vessel containing 59.8 g of water at 24.8°C. What is the final temperature of the system?

## Q6

A 30.5 g sample of an alloy at 93.0°C is placed into 50.0g of water at 22.0°C in insulated coffee cup. If the final temperature of the system is 31.1°C , what is the specific heat capacity of the alloy?

## Q7

For the following reaction: 1/8 S8 (s) + H2 (g) à H2S (g) ∆H = -20.2 kJ

1. Is this an exothermic or endothermic reaction?
2. What is ∆H for the reverse reaction?
3. What is ∆H when 3.2 mol of S8 reacts?
4. What is ∆H when 20.0g of S8 reacts?

### Q8

For the following reaction:

$MgCO_{3\;(s)} \rightarrow MgO_{(s)} + CO_{2\; (g)}$

with ∆H = 117.3 kJ

1. Is heat absorbed or released in the reaction?
2. What is ∆H for the reverse reaction?
3. What is ∆H when 5.35 mol of CO2 reacts with excess MgO?
4. What is ∆H when 35.5 g of CO2 reacts with excess MgO?