Answer to Question #141796 in General Chemistry for Amna

Question

What is the mass of oxygen in 111.144g of ca(oh)2

Answer 1

Q141796,

What is the mass of oxygen in 111.144g of Ca(OH)₂?

Solution:

We can find the mass of oxygen in given grams by Ca(OH)₂ by following three steps.

Step 1: Convert 111.14g Ca(OH)₂ to moles using molar mass of Ca(OH)₂.

Step 2: From moles of Ca(OH)₂ find the moles of O .

Step 3: Convert moles of O to grams using atomic mass of O.

Step 1: Convert 111.14g Ca(OH)₂ to moles using molar mass of Ca(OH)₂.

Molar mass of Ca(OH)₂ = 1 * atomic mass of Ca + 2 * atomic mass of O + 2 * atomic mass of H

= 1*40.078g/mol + 2* 15.999g/mol + 2* 1.0079g/mol

= 40.078g/mol + 31.998g/mol + 2.0158g/mol

= 74.0918g/mol

moles of Ca(OH)₂ = 111.14g Ca(OH)₂ * 1mol Ca(OH)₂ /74.0918g Ca(OH)₂

= 1.5000 mol of Ca(OH)₂

Step 2 : Find moles of O present in 1.5000 mol of Ca(OH)₂

Each unit of Ca(OH)₂ contains 2 atoms of O.

So 1mole of Ca(OH)₂ will contain 2 mole of O.

Using this we can find the moles of O in 1.500 mol of Ca(OH)₂ .

Moles of O = 1.5000 mol of Ca(OH)₂ * 2 mol of O / 1 mol of Ca(OH)₂

= 3.0000 mol of O.

Step 3: Convert 3.0000 moles of O to grams using atomic mass of O.

Atomic mass of O = 15.999g/mol

grams of O = 3.0000 mol of O * 15.999 g of O/ 1mol of O = 47.9997 g of O.

so the mass of O present in 111.144g of Ca(OH)₂ is 47.9997grams.

In question we are given 111.144g in 6 significant figure, so our final answer is also in

6 significant figure.