IB Chemistry 11 Energetics WS Name: _____________ Enthalpy Changes

1. It takes 78.2 J to raise the temperature of 45.6 g lead by 13.3°C. Calculate the specific heat capacity of lead.

2. How much heat energy is required to increase the temperature of 10.0 g of nickel (specific heat capacity of

440 J kg-1K-1) from 50.0 °C to 70.0 °C?

3. Copper has a specific heat capacity of 400 J kg-1K-1. If a 50 g cylinder of copper absorbs 800 J of energy,

by how much will its temperature rise?

4. The enthalpy of combustion of ethanol is 1370 kJ mol-1 . How much heat is released when 0.200 moles of

ethanol undergo complete combustion?

Bond Enthalpies

1. Using the bond enthalpies found in the IB Data Booklet Table 10, calculate the ΔH for the following reaction:

H2C=CH2 + H2 à H3C-CH3 (Note: The equation is written to highlight that the carbon to carbon bond goes from a double bond to a single bond.)

2. Using the bond enthalpies found in the IB Data Booklet Table 10, calculate the ΔH for the following reaction:

3. Using the bond enthalpies found in the IB Data Booklet Table 10, calculate the ΔH for the complete combustion

of methane (CH4). (Hint: Be sure to draw the structures of all of the molecules out, because you need to know

where there are single and double bonds!)

Hess’s Law

1. Calculate the change in enthalpy for the following reaction: 2C (s) + 2H2(g) à C2H4 (g)

Given: I. C (s) + O2 (g) à CO2 (g) ΔH = - 395 kJ

II. H2(g) + ½ O2 (g) à H2O (l) ΔH = - 287 kJ

III. C2H4 (g) + 3 O2 (g) à 2CO2(g) + 2H2O (l) ΔH = -1416 kJ

2. Given the following equation of interest:

2 CH4(g) + 3½ O2(g) à (COOH)2 (s) + 3H2O (l)

And given:

I. CH4(g) + O2 (g) à HCHO (l) + H2O (l) ΔH = x

II. HCHO (l) + ½ O2 (g) à HCOOH (l) ΔH = y

III. 2 HCOOH(l) + ½ O2 à (COOH)2(s) + H2O(l) ΔH = z

How would the ΔH for the equation of interest, be represented using x, y, and z?