Question

The standard enthalpies of formation for solid sodium carbonate, aqueous sodium ion, aqueous carbonate ion, and liquid water are -1131 kJ, -240.1 kJ, -677.1 kJ, and -285.8 kJ, respectively. If 5.00 g of solid sodium carbonate at 25.0°C is dissolved in 50.0 g of liquid water, also initially at 25.0°C, immediately after dissolution is complete will the temperature of the resultant solution be greater than, less than, equal to, or cannot be determined compared with 25.0°C? Justify your choice.

Answer 1

2 Na (s) + c (s) + 3/2 O_2 (g) rightarrow Na_2 CO_3 (s) OH_F = -1131 kJ Na_2CO_3 (s) rightarrow 2 Na (s) + c (s) + 3/2 O_2 (g) Delta H_rxn = 1131 kJ - (1) Na (s) rightarrow Na^+ (ae) Delta H_F = -240.1 kJ c (s) + 3/2 O_2 (g) + 2 e rightarrow CO_3^2- (ar) Delta H_F = -677.1 kJ - (2) H_2 + 1/2 O_2 rightarrow H_2O () Delta H_F = -285.8 kJ 2 Na (s) rightarrow 2Na^+ (ar) Delta H = -(2 times 240.1 kJ) - (3) Na_2 CO_3 (s) rightarrow 2 Na^+ (ar) + CO_3^2 - 1 (ar) From equation (1), (2) & (3) Delta H_rxn = 1131 + (-677.1) - (2 times 240.1) = = -26.3 reaction is exothermic, temp of solution increase Ans Greater than