Question

If 56 g of calcium oxide reacts with a certain amount of water (X g), a new compound with mass 74 g is formed. The value of X (in g) is

• A.
  130
• B.
  92
• C.
  18
• D.
  8

Answer 1

The correct option is C

18
According to the law of conservation of mass, the total mass of the reactants must be equal to the total mass of the products.

Mass of calcium oxide + Mass of water = Mass of new compound

$56+X=74\Rightarrow X=74–56=18g$

Hence, the correct answer is option (c).