Hess Law Practice Problems
Quiz by Amoi Salmon
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- Q1Which of the following is an example of Hess Law?Calculating the enthalpy change of a reaction by adding the enthalpy changes of two or more reactions.Finding the molar mass of a substance by measuring its density.Using stoichiometry to calculate the amount of reactant needed in a reaction.Determining the equilibrium constant of a reaction by measuring the concentrations of reactants and products.30s
- Q2What is the symbol for enthalpy change?ΔEΔSΔHΔG30s
- Q3What does a negative enthalpy change, ΔH, indicate?That the reaction is exothermic.That the reaction does not involve a change in enthalpy.That the reaction is at equilibrium.That the reaction is endothermic.30s
- Q4What is the enthalpy of reaction for the reverse of a reaction (flipped)?The negative of the enthalpy of the forward reaction.The same as the enthalpy of the forward reaction.Zero.It cannot be determined.30s
- Q5What is the enthalpy of reaction for a reaction that has two or more reaction steps?The sum of the enthalpy changes of the individual reaction steps.It cannot be determined.Zero.The difference of the enthalpy changes of the individual reaction steps.30s
- Q6
A + B ----> 2C ΔH = 50kJ
D+ 2C----> E ΔH = 25kJ
What is the ΔH of the overall reaction: A+ B + D-----> E ?
100kJ
75kJ
25kJ
50kJ
30s - Q7
What is the ΔH of the overall reaction: 2A+ 5B ----> 2C + 4D
A + 2B ---> C ΔH = -80kJ
A + 3B ---> C + 4D ΔH = -55kJ
25kJ
135kJ
-25kJ
-135kJ
30s - Q8
(3) Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: PCl3(l) + Cl2(g)→ PCl5(s)
2PCl3(l) → 2P(s) + 3Cl2(g) ΔH = 640 kJ
2P(s) + 5Cl2(g) → 2PCl5(s) ΔH = -886 kJ
123kJ
-123kJ
-246kJ
246kJ
30s - Q9
Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: CuCl2(s) + Cu(s) → 2CuCl(s)
CuCl2(s) → Cu(s) + Cl2(g) ΔH = 206 kJ
2Cu(s) + Cl2(g) → 2CuCl(s) ΔH = -136 kJ
342kJ
70kJ
-70kJ
-342kJ
30s - Q10
What type of reaction is the following reaction and why?
P4(s) + 6Cl2(g) → 4PCl3(g) ΔH = -2439 kJ
Exothermic because ΔH is positive
Endothermic because ΔH is positive
Endothermic because ΔH is negative
Exothermic because ΔH is negative
30s