What is the general formula for a straight-chain alkane? cnhn cnh2n+2 cnhn+2 cnh2n?

Option B:

Alkane is defined as series of hydrocarbons which are saturated (all the carbon-carbon bonds are single) for example: methane, ethane, propane etc.

In alkane, carbon has 4 valence electrons so, it can make single bonds with 4 hydrogen atoms.

In the series, the first alkane is methane, it has 1 carbon atom thus, 4 hydrogen atoms are attached to it and molecular formula becomes . Similarly, the second alkane in the series is ethane, it has 2 carbon atoms, both attached with single bond. The remaining three electrons in each carbon are shared with 3 hydrogen atoms each thus, it has total of 6 hydrogen atoms. Molecular formula of ethane will be .

Now, for general formula, let the number of carbon atoms be n thus, number of hydrogen atoms will be

Therefore, general formula of straight chain alkane is .

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2