Question

Can you answer 2 to 5?

Post-Laboratory Questions Use the spaces provided for the answers and additional paper if necessary.) A student was given only one graduated cylinder3. The accepted &Hheutan of hydrobromic acid experiment. After using it to measure (HBr) reacting with NaOH solution and of HNO he student failed to reacting with potassium hydroxide (KOH) solution 50.0 mL of the assigned acid, t rinse or dry the cylinder before measuring out the are identical. 50.5 mL of the base. Would the calculated &Hneutan be higher, lower, or the same as the literature aqueous HBr and HNOs have in common (1) Write net ionic equations to show what Heutan? Briefly explain this difference as a result of using only one graduated cylinder for the experi- ment. (2) State what aqueous NaOH and KOH have in common. 2. Explain how the following changes in the proce- dure for this experiment would affect the results. (1) A glass beaker was used instead of a pressed polystyrene cup. (3) Explain why you would expect that Aeutzn for HBr reacting with NaOH solution and AHheutan for HNO3 reacting with KOH solution would be identical. Write appropriate equations to support this explana- tion. (2) A pressed polystyrene top was used to cover the polystyrene cup after the acid and base solutions had been mixed date

Answer 1

1. (a) As the actual volume of base ( 50.5 mL) is more than the volume noted for calculation (50 mL), the actual mass of the base solution is more than the calculated mass. The calculated value of enthalpy chage is less than actual one as enthalpy change is directly proportional to mass of the solution.

2. (a) A glass beaker would allow the heat to be released in the surrounding and the calculated enthalpy change is less than actual.

(b) The polystyrene top would absorb some heat as well and the calculated value of enthalpy change is less than actual.

3. (a) the net ionic equation is:

H⁺ (aq) + OH^- (aq) = H₂O (l)

Both HBr and HNO3 have H⁺ ion in common.

(b) Both KOH and NaOH have OH^- in common.

(c) Both the reactions involve the neutralisation of strong acid and base and the net ionic equation is same for both cases. The neutralisation happens between H+ and OH- and for the reason the enthalpy of neutralisation is same for both cases.