AP Chem Unit 4 In Class Review

Front

What is the enthalpy change (ΔH) for the reaction 2C(s) + 2H2(g) → C2H4(g)?

Back

ΔH = +52.4 kJ/mol

Front

How much heat is released or absorbed when 0.20 mol of C(s) is formed from C2H4(g)?

Back

5.24 kJ is released.

Front

What is the heat of formation of water based on the electrolysis reaction 2H2O(l) → 2H2(g) + O2(g) with ΔH = +570 kJ/mol?

Back

-285 kJ/mol

Front

What is the value of ΔH in kJ per mole of NaOH reacted when 4.0g of NaOH reacts with excess HCl releasing 5.7 kJ of heat?

Back

-57 kJ/mol

Front

In which direction does heat flow to reach thermal equilibrium between two gas samples?

Back

From high temperature to low temperature.

Front

At which point in a heating curve does the sample contain the most gas?

Back

Point E.

Front

Define enthalpy (H).

Back

Enthalpy is a measure of the total energy of a thermodynamic system, including internal energy and the energy required to displace its environment.

Front

What is the significance of a positive ΔH value?

Back

A positive ΔH indicates that the reaction is endothermic, meaning it absorbs heat from the surroundings.

Front

What does a negative ΔH value indicate?

Back

A negative ΔH indicates that the reaction is exothermic, meaning it releases heat to the surroundings.

Front

What is thermal equilibrium?

Back

Thermal equilibrium is the state in which two objects in contact with each other cease to exchange energy by heat.