Question

67. The chemical analysis of a compound having molecular mass 188 gives, C= 12.8%,
H-2.1% and Br=85.1% its molecular formula is:
D. CH2(Br)2
B. C2H4Br3
E. C2H2(Br)3,
A. CH2Br
C. C2H4Br

Answer 1

Answer:

D. CH2(Br)2

Explanation:

molecular mass of bromine is ~80 and 85% of 188 is ~160. therefore Br2. you can similarly check for others

Answer 2

Answer:

The molecular formula is C2H4Br2.

Given:

• Mass of H = 2.1 g
• Mass of C = 12.8 g
• Mass of Br = 85.1 g

To Find:

• The moelcular formula.

Solution:

Find the masses of the elements.

=> Mass of C = 1.07 moles.

=> Mass of H = 2.1 moles.

=> Mass of Br = 1.07 moles.

For the mole ratio, divide each value of moles by the smallest number of moles calculated.

Now,

For C = 1.07/1.07 = 1

For H = 2.1/1.07 = 2

For Br = 1.07/1.07 = 1

The ratio of C : H : Br = 1 : 2 : 1.

Therefore,

• Empirical formula is CH2Br.

=> Empirical formula = 1 × 12 + 2 × 1 + 1 × 79.9

=> 93.3 g

Molecular mass = 187.9

Molecular formula = C2H4Br2.