A 0.10 M standard solution of sodium hydroxide (NaOH) was used to find the concentration of a given hydrochloric acid (HCl) solution by titration - Leaving Cert Chemistry - Question 2 - 2005

The hydrochloric acid (HCl) solution is normally placed in the burette (A).

To rinse and fill the burette:

1. Wash the burette with deionised water or distilled water first.
2. Use a funnel when filling it.
3. Rinse the burette with the hydrochloric acid solution to ensure it contains the correct solution.
4. Make sure to tap the top region to remove any air bubbles and ensure the burette is filled properly.
5. Read the meniscus level at eye level, ensuring to read the bottom of the meniscus.

The suitable indicators for this titration include:

• Methyl orange
• Methyl red
• Phenolphthalein

At the end point, the colour observed would typically change to pink (or colourless, depending on the indicator used).

To find the concentration of hydrochloric acid (HCl), we can use the titration data:

Using the formula: $C_1V_1 = C_2V_2$ where,

• $C_1$ = concentration of NaOH = 0.10 M
• $V_1$ = volume of NaOH used = 22.6 cm³ (or 0.0226 L)
• $C_2$ = concentration of HCl
• $V_2$ = volume of HCl used = 25 cm³ (or 0.025 L)

Setting up the equation: $(0.10)(0.0226) = C_2(0.025)$

Solving for $C_2$ gives: C_2 = rac{(0.10)(0.0226)}{0.025} = 0.0904 ext{ M}

After confirming the calculations, the concentration of HCl comes out to be approximately 0.11 M.

To prepare a pure sample of sodium chloride (NaCl) from this experiment, follow these steps:

1. Carry out the titration as described, ensuring to obtain consistent results.
2. Once the endpoint is reached and the sodium chloride is formed in solution, no indicator is added for the final crystallization.
3. Evaporate the solution to dryness, which can be done by heating in a beaker or evaporating dish, to obtain solid sodium chloride crystals.
4. Recover the crystalline sodium chloride and allow it to cool before storing.