Which of the following methods is NOT suitable for concentrating a protein solution?

1 gram of sodium hydroxide is neutralized with excess hydrochloric acid. If 0.73 g of sodium chloride is formed, what is the percentage yield of the reaction?

1 gram of potassium hydroxide was treated with $20 \mathrm{mL}$ of $0.5 \mathrm{M}$ HCl solution. The mass of potassium hydroxide left unreacted is equal to

0.5 grams of sodium hydroxide was treated with $12.5 \mathrm{mL}$ of $0.75 \mathrm{M}$ HCl solution. The mass of sodium hydroxide left unreacted is equal to

2 grams of sodium hydroxide was treated with $50 \mathrm{mL}$ of $0.75 \mathrm{M}$ HCl solution. The mass of sodium hydroxide left unreacted is equal to

1 gram of sodium hydroxide was reacted with $25 \mathrm{mL}$ of $0.75 \mathrm{M}$ sulfuric acid ($\mathrm{H_2SO_4}$). What mass of sodium hydroxide remains unreacted?