Question

EXPERIMENT Provided Materials and Equipment: General glassware found in the lab or in your drawer/locker 60 mL of 0.1 M HCl(aq) 60 mL of 0.1 M NaOH(aq) pH electrode and storage solution Logger Pro software Standard buffers for calibration pH 4.00 and pH 7.00 2 burets (per group of 4 students) Four solutions to test

Answer 1

In the given experiment, the aim is mostly to study and compare the differences in the acid and base buffering capacity of water, eye saline, listerine, ice tea.

Using the formula given for acid capacity of buffer and base capacity of buffer, let's first calculate the same for each of them.

	Acid capacity of buffer	Base Capacity of buffer
Water	24 * 0.1/ 6.36 * 25 = 0.015	10.1 * 0.1 / 6.32 * 25 = 0.0064
Eye Saline	8 * 0.1/ 6.04 * 25 = 0.0053	10.5 * 0.1 / 1.28 * 25 = 0.033
Listerine	10.3 * 0.1 / 2.35 * 25 = 0.017	18.1 * 0.1 / 9.24 * 25 = 0.0078
Ice tea	6.2 * 0.1 / 1.55 * 25 = 0.016	14.7 * 0.1 / 8.45 * 25 = 0.0069

Explaining the above calculation,

For acid capacity of water,

Volume of acid added is 24mL; 6.36 is the change in pH units; 25mL is the volume of buffer taken.

Thus, moles of acid needed to change pH by 1 unit is - (24mL* 1litre * 0.1moles/ litre ) / 1000mL * 6.36 pH units = 0.00037moles

volume of buffer taken in litre = 25/1000 = 0.025 litre

Acid capacity of buffer = 0.00037 / 0.025 = 0.015 moles / litre

Similar calculations are done for the rest too.

Thus, water, listerine and ice tea have better acid capacity of buffer. While eye saline has better base buffer capacity.