Question

1. Calculate the mass fraction stochiometric ratio for the combustion of

n-Butane (C₄H₁₀) in air ( 20% v/v O₂   80% v/v N₂)* ratio 4:1.

Given the following Atomic Weights for the elements and their valencies.*

Element            Symbol         Atomic Weight           Valency

Hydrogen              H                          1                             1

Carbon                  C                         12                            4

Nitrogen                N                         14                            3

Oxygen                  O                         16                            2

*Note these numbers have been rounded for ease of calculation.

Answer 1

combustion reaction occurs when hydrocarbon reacts with oxygen to produce carbon dioxide and water.

the balanced combustion reaction equation for butane is:

from the equation we get:

for 1 mol , we require 13/2 mol of .

stoichiometric ratio in terms of mass is determined by multiplying moles of a compound with its molecular mass.

molecular mass of   = 4(12 g\mol) + 10(1 g\mol) = 58 g\mol

molecular mass of   = 2(16 g\mol) = 32 g\mol

and air are in ratio 4:1

let, mixture contains 400 mol of and 100 mol of air

400 mol of =

we know that volume % = mole %

100 mol of air contains:

= 0.2(100 mol) = 20 mol =

= 0.8(100 mol) = 80 mol =

total mixture mass = 23200 g + 640 g + 2240 g = 26080 g

formula for mass fraction is :

=

=

=