A gaseous alkane on complete combustion gives CO2 and H2O . If the ratio of moles of O2 needed for combustion and moles of CO2 formed is 5:3. find out the formula of alkane.

Question

A gaseous alkane on complete combustion gives CO2 and H2O . If the ratio of moles of O2 needed for combustion and moles of CO2 formed is 5:3. find out the formula of alkane. (A) C4H10 (B) C5H12 (C) C3H8 (D) C2H6

Tardigrade Admin · Accepted Answer

Let the alkane be CnH2 n + 2 CnH2 n + 2+[n + (n + 1 /2)]O2 arrow nCO2+(.n+1.)H2O (M o l e o f O2/M o l e o f C O2 )=(n + (n + 1 /2)/n)=(5/3) n=3 Thus the alkane is C3H8

Q. A gaseous alkane on complete combustion gives $C O_{2} an d H_{2} O$ . If the ratio of moles of $O_{2}$ needed for combustion and moles of $C O_{2}$ formed is $5 : 3.$ find out the formula of alkane.

$C_{4} H_{10}$

$C_{5} H_{12}$

$C_{3} H_{8}$

$C_{2} H_{6}$

Let the alkane be $C_{n} H_{2 n + 2}$

$C_{n} H_{2 n + 2} + [n + \frac{n + 1}{2}] O_{2} \to n C O_{2} + (n + 1) H_{2} O$

$\frac{M o l e o f O _{2}}{M o l e o f C O _{2}} = \frac{n + \frac{n + 1}{2}}{n} = \frac{5}{3}$

$n = 3$

Thus the alkane is $C_{3} H_{8}$

Q. A gaseous alkane on complete combustion gives CO2​andH2​O . If the ratio of moles of O2​ needed for combustion and moles of CO2​ formed is 5:3. find out the formula of alkane.

C4​H10​

C5​H12​

C3​H8​

C2​H6​