CH-400

Burette and pipette readings

Chemistry · Secondary 3 · Hard · Burette and pipette readings

A student titrates

25.0\,\text{cm}^3

of sodium hydroxide with hydrochloric acid. His first three readings of acid volume are

21.40\,\text{cm}^3

21.35\,\text{cm}^3

and

20.10\,\text{cm}^3

.

Which mistake most likely caused the third reading to be much lower than the others?

Not adding the acid drop by drop near the end of titration 3.
Rinsing the burette with water instead of acid before titration 3.
Using $20.0\,\text{cm}^3$ of alkali instead of $25.0\,\text{cm}^3$ in titration 3.
Forgetting to record the initial burette reading for titration 3.

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