Question

What is the percent composition of Ca(OH)2? 37.7% Ca, 53.0% O, and 10.3% H 45.5% Ca, 38.2% O, and 16.3% H 54.0% Ca, 43.0% O, and 2.7% H 64.7% Ca, 27.0% O, and 8.3% H

Answer 1

The molar mass of Calcium hydroxide is 74 g/mol

To find the percent composition we have to find the number of atoms of each element in the formula .

So there’s

Calcium - 1

Oxygen - 2

Hydrogen - 2

Then have to multiply the relative atomic mass of each element by the number of atoms

Ca - 40 g/mol x 1 = 40

O - 16 g/mol x 2 = 32

H - 1 g/mol x 2 = 2

Then To find percent composition of each element we have to divide the mass of each element in the formula by the relative molecular mass of calcium hydroxide

Ca - 40 / 74 x 100 % = 54.0%

O - 32 / 74 x 100 % = 43.2 %

H - 2 / 74 x 100 % = 2.7%

From the options given correct answer is 3rd option

54.0% Ca , 43.0% O and 2.7 % H