Enthalpy Changes
Chemistry ⇒ Thermochemistry and Energetics
Enthalpy Changes starts at 10 and continues till grade 12.
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See sample questions for grade 12
A reaction has ΔH = +150 kJ mol-1. Is the reaction endothermic or exothermic?
A reaction has ΔH = -250 kJ mol-1. Will the temperature of the surroundings increase or decrease?
A student mixes 50.0 g of water at 25°C with a salt, causing the temperature to drop to 20°C. Is the dissolution process endothermic or exothermic?
Calculate the enthalpy change for the reaction: 2H2(g) + O2(g) → 2H2O(l), given ΔH°f[H2O(l)] = -286 kJ mol-1.
Calculate the enthalpy change for the reaction: C(s) + O2(g) → CO2(g), given the following data:
ΔH°f[CO2(g)] = -393.5 kJ mol-1
Calculate the enthalpy change for the reaction: H2(g) + Cl2(g) → 2HCl(g), given bond enthalpies: H-H = 436 kJ mol-1, Cl-Cl = 242 kJ mol-1, H-Cl = 431 kJ mol-1.
Calculate the enthalpy change for the reaction: N2(g) + 3H2(g) → 2NH3(g), given ΔH°f[NH3(g)] = -46 kJ mol-1.
Calculate the enthalpy change when 2 mol of methane (CH4) is burned, given that the standard enthalpy of combustion of methane is -890 kJ mol-1.
Describe how calorimetry can be used to determine enthalpy changes.
Describe the difference between enthalpy of formation and enthalpy of combustion.
Explain why the enthalpy change of neutralization is always negative.
Explain why the enthalpy of atomization for diatomic gases is half the bond dissociation enthalpy.
Explain why the enthalpy of combustion is always negative.
State Hess's Law.
State the equation relating enthalpy change (ΔH), internal energy change (ΔU), pressure (P), and volume change (ΔV) at constant pressure.
