Grade 9 Science: Heat of Formation
This worksheet focuses on understanding and calculating the standard heat of formation in chemical reactions for Grade 9 science students.
Includes
Standards
Heat of Formation Worksheet
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Read each question carefully and answer to the best of your ability. Show all your work for calculation questions.
1. What is the standard heat of formation (ΔH°f) for a pure element in its standard state?
Always positive
Always negative
Zero
Depends on the element
2. An endothermic reaction is characterized by:
Release of heat
Absorption of heat
No change in heat
Formation of a precipitate
3. The heat of formation is the change in enthalpy when one mole of a compound is formed from its constituent in their standard states.
4. A reaction with a negative ΔH°f is classified as an reaction.
5. Explain the difference between an exothermic and an endothermic reaction in terms of heat flow and the sign of ΔH.
6. The standard heat of formation for O2(g) is 0 kJ/mol.
True
False
7. Calculate the enthalpy change (ΔH°) for the following reaction using the given standard heats of formation:
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
Given:
ΔH°f [CH4(g)] = -74.8 kJ/mol
ΔH°f [CO2(g)] = -393.5 kJ/mol
ΔH°f [H2O(l)] = -285.8 kJ/mol