Question

How many bromine atoms are present in 26.0 g of CH2Br2 ??

Answer 1

In this problem we are given mass of CH2Br2. We find its moles by using molar mass. Then we compare the moles or find mole ratio between CH2Br2 and Br. By using mole ratio we can get moles of Br.

Once we get moles of Br then we can multiply it by avagadro’s number and get total number of Br atoms in given mass of CH2Br2

Solution:

Given mass of CH2Br2 = 26 g

Molar mass of CH2Br2 = 173.83 g/ mol

Number of moles =26 g / 173.83 g per mol = 0.1496 mol

Mole ratio CH2Br2 : Br   is 1 : 2

Therefore moles of Br = mol CH2Br2 x 2 mol Br/1 mol CH2Br2= 0.1496 mol x 2 mol Br / 1 mol CH2Br2

= 0.299 mol Br

Number of Br atoms = 0.299 mol Br x 6.02 E23 Br atoms / 1 mol Br

= 1.8 E23 Br atoms