Calculate the formula unit mass of magnesium hydroxide, Mg(OH)2. Class 9

Calculate the formula unit mass of magnesium hydroxide, Mg(OH)₂. Class 9

Question 1.

Calculate the formula unit mass of magnesium hydroxide, Mg(OH)₂. Class 9

Answer:

Atomic mass of magnesium = 24 u, oxygen = 16 u, hydrogen = 1 u

Magnesium hydroxide has one atom of magnesium, two atoms of oxygen and two atoms of oxygen

Formula unit mass of Mg(OH)2 = atomic mass of Mg + 2(atomic mass of 0) + 2(atomic mass of H)

= (1 × 24) + (2 × 16) + (2 × 1) = 58 u

Question 2.

Calculate the formula unit mass of calcium chloride, CaCl₂. Class 9

Answer:

Atomic mass of calcium = 40 u, chlorine = 35.5 u

Calcium chloride has one atom of calcium and two atoms of chlorine.

Formula unit mass of calcium chloride = atomic mass of Ca + 2 (atomic mass of Cl)

= (1 × 40) + (2 × 35.5) = 111 u

Question 3.

Calculate the formula unit mass of sodium chloride (NaCl). Class 9

Answer:

Atomic mass of sodium = 23 u, chlorine = 35.5 u

Sodium chloride has one atom of sodium and one atom of chlorine.

Formula unit mass of sodium chloride = atomic mass of Na + atomic mass of Cl

= (1 × 23) + (1 × 35.5) = 58.5 u