Question

Consider the given reaction sequence:
$A\to B\text{(Yield = 40\%)}$
$B\to 2C\text{(Yield = 70\%)}$
$3C\to 4D\text{(Yield = 50\%)}$
The number of moles of D formed if there are 4 mol of A to begin with is:

• A. 3.23 mol
• B. 2.98 mol
• C. 1.25 mol
• D. 1.50 mol

Answer 1

The correct option is D 1.50 mol

$A\to B\dots \text{(i)}$
$B\to 2C..\text{(ii)}$
$3C\to 4D\dots \text{(iii)}$
In reaction (i),
1 mol A produces 1 mol of B
So, 4 mol of A will produce 4 mol of B
Yield of the reaction is 40 %
Actual amount of B formed $=4\times 0.4=1.6$ moles
In reaction (ii),
1 mol of B produces 2 mol of C
1.6 mol of B will produce 3.2 mol of C
Yield of the reaction is 70 %
Actual amount of C formed $=3.2\times 0.7=2.24$ moles
In reaction (iii),
3 moles of C produce 4 moles of D
2.24 moles of C will produce $\left(4/3\right)\times 2.24=2.99$ moles
Yield of the reaction is 50 %
Actual amount of D formed $=2.99\times 0.5=1.50\text{moles}$