Question

Complete combustion of $3g$ of ethane gives x $\times {10}^{22}$ molecules of water. The value of x is _____ [Round off to the Nearest Integer].
[Use: $N_A=6.023\times {10}^{23};$ Atomic masses in u : C : 12.0; O : 16.0 : H : 1.0 ]

Answer 1

Answer: 18
$\underset{3g}{C_2{H}_6}+O_2\to 2C{O}_2+3H_{2}O$
Moles of $C_2{H}_6=\frac{3}{30}=0.1$
$\underset{0.1mol}{C_2{H}_6}+O_2\to 2C{O}_2+\underset{0.3mol}{3H_{2}O}$

$\text{No. of molecules of}{H}_{2}O=0.3\times 6.023\times {10}^{23})$
$=1.8069\times {10}^{23}$
$=18.069\times {10}^{22}$