Core practical 2 - find the concentration of a solution of sodium hydroxide

A 250cm³ volumetric flask has an accuracy ±0.6 cm³ . Calculate the percentage uncertainty in the volume of the sulfamic acid solution in the volumetric flask.

0.6/250 × 100 = 0.24%

Each burette reading is accurate to ±0.05cm³. Calculate the percentage uncertainty in one of your titres.

0.05 × 2/titre selected × 100

Why should the pipette be rinsed with the sodium hydroxide solution after washing it with water?

Water left in pipette will dilute the sodium hydroxide solution, changing the number of moles used.

Why is there no need to dry the conica flask after washing it out between trials?

The water will not change the number of moles of sodium hydroxide – its volume is measured before it is put into the flask.

Identify another indicator that could be used in this titration and state the colour change that would be seen at the end point.

Phenolphthalein, it changes from pink to colourless.