ICSE Class 10 Chemistry 2014 Solved Paper

Question : 33 of 88

Marks: +1, -0

A compound made up of two elements

X

and

Y

has an empirical formula

X_2

Y

. If the atomic weight of

X

is 10 and that of

Y

is 5 and the compound has a vapour density 25 , find its molecular formula.

Solution:

Emp. formula

=X_2 Y

, At. wt. of

X=

10, At. wt. of

Y=5

∴

Empirical formula mass

=2 × 10+5=25

vapour density V.D.

=25

\;\text " Mol. Mass "\;\;=\;\text " V.D. "\; × 2=25 × 2

\;=50

n\;=\;{\;\text " Mol. Mass "\;}/{\;\text " Emp. formula mass "\;}

\;=\;{50}/{25}=2

\;\text " Mol. formula "\;\;=\;\text " Emp. formula "\; × 2

\;= {\X}_2 {\Y} × 2

\;= {\X}_4 {\Y}_2 .

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