A certain amount of sodium reacts with plenty of water. The H 2 gas collected from this reaction was 589 mL at 21 ° C and 135 mmHg. The final solution (NaOH) is titrated by 20.34 mL of a standard HCl solution. NaOH ( aq ) + HCl ( aq ) !→ H 2 O ( l ) + NaCl ( aq ) (a) Calculate the molarity of the HCl solution. (b) Calculate the mass of sodium that reacts with water.
6. (10 points) From the following data, H 2 (g) ⇒ 2 H (g) Δ H° = 436.4 kJ/mol Br 2 (g) ⇒ 2 Br (g) Δ H° = 192.5 kJ/mol H 2 (g) + Br 2 (g) ⇒ 2 HBr (g) Δ H° = –72.4 kJ/mol calculate the enthalpy change ( Δ H°) for the following reaction H (g) + Br (g) ⇒ HBr (g) 7. (12 points) The enthalpy of combustion of unknown sample is measured using a constant-pressure bomb calorimeter. When 2.783 g of the unknown sample are burned in the calorimeter, the temperature of the system rises from 21.00 ° C to 25.33 ° C. The quantity of water surrounding the bomb is 2.000 × 10 3 g. The heat capacity of bomb is 5.32 kJ/ ° C. The specific heat for water is 4.184 J/g ! ° C. What is the enthalpy of combustion of the unknown sample in kJ/g?
8. (10 points) Ice at 0 ° C is placed in a Styrofoam cup containing 415 g of water at 21.5 ° C. The specific heat of water is 4.184 J/(g ⦁ °C). Some ice remains after the ice and water reach an equilibrium temperature of 0 ° C. It takes 334 J to melt 1g of ice at 0 ° C. Determine the mass of ice that has melted. Ignore the heat capacity of the cup.