Question

If your lab procedure instructs you to add two parts of acid to each one part of water and you start with 25 ml of water, how much acid will you add, and how will you add it

Answer 1

When the ratio is given in parts, there is no strict rule on the units of measurement. It is a general term that is applicable to any unit. For example, the unit here is in mL. Since the ratio is 2 parts acid to 1 part water, that is also equivalent to 2 mL acid to 1 mL water. Hence, you have to add 2 mL of acid to water, not vice versa. Other acids are highly reactive to water. So, you have to add the acid slowly to avoid violent reactions.