Chemistry Enthalpy Problems Questions PDF

Preview

Summary

Chemistry Enthalpy Problems Questions...

Description

ENTHALPY PROBLEMS Specific heat capacity of water (and most dilute solutions) = 4.2 kJ kg -1 K-1 or 4.2 J g-1 K-1. Remember 1 ºC change is the same as 1 K change in temperature. 1.

When a sample of 0.022 mol of methanol was burnt completely in air, the heat from the reaction raised the temperature of 140 g of water by 15ºC. Calculate the enthalpy change if one mole of methanol was burned.

2.

When 25.0 g of hydrated copper (II) sulphate (CuSO4.5H2O) was dissolved in 200 g of water the temperature fell by 1.4ºC. Calculate the enthalpy change in kJ mol-1.

3.

The important metal manganese can be extracted from its oxide using carbon oxide. Mn2O3(s) + 3CO(g) = 2Mn(s) + 3CO2(g) Using the data for the standard enthalpies of formation below, calculate the enthalpy change for the reaction. Standard enthalpy of formation (kJ mol-1) Mn2O3(s) -971, CO(g) -111, Mn(s) 0, CO2(g) -394

4.

The important industrial chemical calcium hydroxide can be made by the following reaction. CaO(s) + H2O(l) = Ca(OH)2(s) Using the data for the standard enthalpies of formation below, calculate the enthalpy change for the reaction. Standard enthalpy of formation (kJ mol-1) CaO(s) -635.1, H2O(l) -285.8, Ca(OH)2(s) -986.1

5.

Methane can be formed from carbon and hydrogen. C(s) + 2H2(g) = CH4(g) Use the enthalpy of combustion data given to calculate the enthalpy of formation of methane. Standard enthalpy of combustion (kJ mol-1) C(s) -394, H2(g) -286, CH4 --890

6.

The standard enthalpy of formation of glucose (C 6H12O6) cannot be found directly by experiment. Use the enthalpy of combustion data given to calculate its value. You will first need to write an equation to describe the formation of glucose from its elements in their standard states. Standard enthalpy of combustion (kJ mol -1) data C(s) -394, H2(g) -286, C6H12O6 -2801

7.

Use the bond enthalpy data to calculate the enthalpy change for the following reaction. 2H2(g) + O2(g) = 2H2O(g) E(H-H) 436, E(O=O) 497, E(O-H) 463 all values kJ mol -1

8.

Use the bond enthalpy data to calculate the enthalpy change for the following reaction. C2H6(g) + Cl2(g) = C2H5Cl(g) + HCl(g) E(C-H) 413, E(C-C) 347, E(C-Cl) 346, E(Cl-Cl) 243, E(H-Cl) 432 all values kJ mol-1

9.

The addition of hydrogen to ethene is an exothermic process whose equation is shown below: ∆H = -136 kJ mol -1.

Bond enthalpy values for some bonds are E(C-C) 348, E(C=C) 612, E(H-H) 436, all values kJ mol -1 Use the information to calculate a value for the bond enthalpy of the C-H bond....