The general formula of alkanes is #C_nH_(2n+2)#
Let's apply the formula for the compound #CH_2O#. Here #C# = 1, #H# = 2. But from the alkane general formula, #H# should have been equal to #2n + 2# = #4#. The calculation is as follows:
#2n + 2#
= #2(1) + 2#
= #2 + 2#
= #4#
Let's apply the formula for the compound #C_3H_4#. Here #C# = 3, #H# = 4. But from the alkane general formula, #H# should have been equal to #2n + 2# = #8#. The calculation is as follows:
#2n + 2#
= #2(3) + 2#
= #6 + 2#
= #8#
And now, let's apply the formula for the compound #C_6H_14#. Here #C# = 6, #H# = 14. This fits the number of #C# and #H# atoms calculated from the general alkane formula.
#2n + 2#
= #2(6) + 2#
= #12 + 2#
= #14#
As the formula #C_nH_(2n+2)# fits the compound #C_6H_14# as calculated above, we can say that #C_6H_14# is an alkane.
Hope this helps!
