Question

Write the formula of each compound, and determine its molecular (formula) mass: (a) sodium dichromate; (b) ammonium Perchlorate; (c) magnesium nitrite trihydrate.

Answer 1

Answer:

(a)  Na₂Cr₂O₇ , 262 g/mol

(b) NH₄ClO₄, 117.5 g/mol

(c) Mg(NO₂)₂.3H₂O, 170.3 g/mol

Explanation:

(a) Sodium dichromate

The formula for the compound is: Na₂Cr₂O₇

Calculation of the molecular mass as:

Molar mass of sodium = 23 g/mol

Molar mass of chromium = 52 g/mol

Molar mass of oxygen = 16 g/mol

So, Molecular mass of sodium dichromate  = (23×2) + (52×2) + (16×7) = 262 g/mol

(b) ammonium Perchlorate

The formula for the compound is: NH₄ClO₄

Calculation of the molecular mass as:

Molar mass of nitrogen = 14 g/mol

Molar mass of hydrogen = 1 g/mol

Molar mass of chlorine = 35.5 g/mol

Molar mass of oxygen = 16 g/mol

So, Molecular mass of ammonium Perchlorate  = (14×1) + (1×4) + (35.5×1) + (16×4)= 117.5 g/mol

(c) magnesium nitrite trihydrate

The formula for the compound is: Mg(NO₂)₂.3H₂O

Calculation of the molecular mass as:

Molar mass of Magnesium = 24.3 g/mol

Molar mass of nitrogen = 14 g/mol

Molar mass of hydrogen = 1 g/mol

Molar mass of oxygen = 16 g/mol

So, Molecular mass of magnesium nitrite trihydrate  = (24.3×1) + (14×2) + (16×7) + (1×6)= 170.3 g/mol