C. How many grams of NaOH (sodium hydroxide) are necessary to make 100

mL of an 18% NaOH solution?

18 g

Explanation:

Remember that 1g is equivalent to 1 ml;

1g = 1 mL

100 g = 100 mL

Therefore in an 18% NaOH solution, for every 100 mL, there is 18 g of dissolved NaOH. This is how we derive the percentage solution;

18 g / 100 g = 18%