Question

In a laboratory experiment, a student placed sodium hydroxide crystals on a watch glass and assembled the titration equipment. Then he prepared a solution of $0.10$M sulfuric acid. He weighed $4$ grams of sodium hydroxide and added it to enough water to make $1$ liter of solution. What might be a source of error in the results of the titration?

• A. Some sulfuric acid evaporated
• B. The sulfuric acid became more concentrated
• C. The NaOH solution gained weight, thus increasing its molarity
• D. The NaOH crystals gained $H_{2}O$ weight, thus making the solution less than $0.1$M
• E. The evaporation of sulfuric acid solution countered the absorption of $H_{2}O$ by the NaOH solution

Answer 1

The correct option is D The NaOH crystals gained $H_{2}O$ weight, thus making the solution less than $0.1$M

Since $NaOH$ is hygroscopic, it absorbs moisture from the atmosphere if left open.

Hence, it is possible that $NaOH$ crystals gained $H_{2}O$ weight, making the solution less than $0.1$ $M$ which caused the error in the results of titration.