Question

Please give answer and explanation !

Consider the following reaction: CH4 (g) + 2O2 (g)----------} CO2(g) + 2H20(g) ^Hr= -890 kj

a) is heat absorbed or evolved in the course of the reaction?

b) Calculate the amount of heat trasnferred when 45g of CH4 is decomposed by this reaction at constant pressure.

c) For the given sample of CH4 the enthalpy change on reaction is 66.8 kj. How many grams of H2O are produced?

d) what is the value of ^Hr for the reverse of the previous reaction? How many KJ of heat are released when 27g of H2O reacts completely with CO2to form CH4 and O2 at constant pressure?

Answer 1

In the given reaction,

a) Heat is evolved in the course of the reaction. This is seen from the -ve sign of the enthalpy of the reaction. delta H = -890 kJ

b) We can see from the above given reaction, 1 mole (16.04 g ) of CH4 gives -890 kJ of heat.

Thus, 45 g would give = (45/16.04) mol x -890 kJ = -2496.883 kJ of heat

c) Given the enthalpy change for the reaction = -66.8 kJ

we can see that 1 mole of CH4 gives 2 moles of H2O in the reaction.

thus, enthalpy change for x g of H2O = -66.8 kJ = (x g /18.0153 g/mol)(-890 kJ / 2 mole of H2O)

                                                         x = 2.70 g of H2O is formed in the reaction

d) delta Hr for the reverse reaction would be +890 kJ.

When 27 g of H2O reacts

enthalpy = (27 g /18.0153 g/mol)(890 kJ / 2)

              = 667.00 kJ of heat is released