40 Equilibrium law

For the reversible reaction A(g) + B(s) <—> C(g) + D(g), what is the unit of its Kc?

• mol dm-3

• mol-1 dm3

• mol2 dm-6

• mol-2 dm6

For the reversible reaction CaO(s) + CO2(g) <—> CaCO3(s), what is the unit of its Kc?

• mol dm-3

• mol-1 dm3

• mol2 dm-6

• mol-2 dm6

For the reversible reaction N2(g) + 3H2(g) <—> 2NH3(g), what is the unit of its Kc?

• mol dm-3

• mol-1 dm3

• mol2 dm-6

• mol-2 dm6

For the reversible reaction H2(g) + I2(g) <—> 2HI(g), what is the unit of its Kc?

• mol dm-3

• mol-1 dm3

• mol2 dm-6

• no unit

For the reversible reaction H2(g) + I2(g) <—> 2HI(g) at a particular temperature, there are 1.00 mol of H2, 2.00 mol of I2 and 3.00 mol of HI when equilibrium is attained. What is the value of its Kc? (Only give numerical answer correct to 3 sig. fig.)

For the reversible reaction N2O4(g) <—> 2NO2(g) at a particular temperature, the Kc is 2.00 mol dm-3. At equilibrium, [NO2] is 4.00 mol dm-3. What is the [N2O4]? (Only give numerical answer correct to 3 sig. fig.)

For the reversible reaction CaCO3(s) <—> CaO(s) + CO2(g)at a particular temperature, the Kc is 0.200 mol-1 dm3. If 1.00 mol of CaCO3(s) is placed in a 2.00 dm3 container at that particular temperature, what is the number of mol of CO2(g) present when equilibrium is attained? (Only give numerical answer correct to 3 sig. fig.)

For a reversible reaction, the value of its Kc is very large. What does it imply?

• Total number of products is larger than the total number of reactants in the chemical equation.

• Rate of forward reaction is very high.

• Conc of products is much higher than conc of reactants in the reaction mixture.

• Backward reaction does not take place.