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Chemistry LibreTexts

Worksheet 2: Heat and Hess

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    76326
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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.

    Q2.1

    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)

    Q2.2

    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)

    Q2.3

    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)

    Q2.4

    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)

    Q2.5

    Calculate the \(\Delta{H_{rxn}}\) for

    \[Ca_{(s)} + \frac{1}{2}O_2 + CO_2 \rightarrow CaCO_3\]

    Given:

    \[Ca + \frac{1}{2}O_2 \rightarrow CaO \;\;\;\;\; \Delta{H} = -635.1 \;kJ\]

    \[ CaCO_3 \rightarrow CaO + CO_2 \;\;\;\;\; \Delta{H} = 178.3\; kJ\]

    Q2.6

    Calculate \(\Delta{H_{rxn}}\) for:

    \[2NOCl \rightarrow N_2 + O_2 + Cl_2\]

    Given:

    \[ \frac{1}{2}N_2 + \frac{1}{2}O_2 \rightarrow NO \;\;\;\;\; \Delta{H} = 90.3\; kJ\]

    \[ NO + \frac{1}{2}Cl_2 \rightarrow NOCl \;\;\;\;\; \Delta{H} = -38.6\; kJ\]