Question

NH, is formed in the following steps:
I:Ca + C ----> CaC2
II: CaC2 + N2 - > CaCN2 +C.
III: CaCN2 + H20 —NH3 + CaCO3
50% yield -I
100% yield-II
50% yield-III
To obtain 2 mol NH3, calcium required is :
(A) 1 moi
(B) 2 mol
(C)3 mol
(D)4mol​

Answer 1

Answer : The correct option is, (A) 1 mole

Explanation :

The balanced chemical reactions are :

I : $Ca+2C\rightarrow CaC_2$

From this reaction we conclude that,

As, 1 mole of Ca react to give 1 mole of $CaC_2$

But the yield is, 50%

So, 1 mole of Ca react to give $\frac{1}{2}$ mole of $CaC_2$

II : $CaC_2+N_2\rightarrow CaCN_2+C$

From this reaction we conclude that,

As, 1 mole of $CaC_2$ react to give 1 mole of $CaCN_2$

But the yield is, 100%

So, $\frac{1}{2}$ mole of $CaC_2$ react to give $\frac{1}{2}$ mole of $CaCN_2$

III : $CaCN_2+3H_2O\rightarrow 2NH_3+CaCO_3$

From this reaction we conclude that,

As, 1 mole of $CaCN_2$ react to give 2 mole of $NH_3$

But the yield is, 50%

So, $\frac{1}{2}$ mole of $CaCN_2$ react to give 1 mole of $NH_3$

Or we can say that,

As, 1 mole of $NH_3$ obtained from $\frac{1}{2}$ mole of $Ca$

So, 2 mole of $NH_3$ obtained from $\frac{2}{2}=1$ mole of $Ca$

Therefore, the moles of Ca required is, 1 mole

Answer 2

Answer:

Option (D) : 4 mol

Explanation:

In the 3rd step,

From 1 mol ofCaCN2 , the amount of yield of NH3 which we predict to come is:

Mass of NH3 (predicted)= moles of NH3 ×MW = 2×17 =34g

But the actual yield is only 50%.

Therefore, Mass of NH3(actual)= 50% × 34g=17g

17 g of NH3 means 1 mole of NH3

Therefore,we can say that in the given question ,

1 mol of CaCN2 will produce 1 mol of NH3........(i)

Similarly,

As even 1st step has 50% yield of product

1 mol of Ca will produce 1/2 mol of CaC2.........(ii)

The second step has 100 % yield. So,

1 mol of CaC2 will produce 1 mol of CaCN2.....(iii)

We have been asked to obtain 2 mol of NH3:

For 2 mol of NH3, 2 mol of CaCN2 are required

[ From(i) ]

For 2 mol of CaCN2, 2 mol of CaC2 are required.

[ From(iii) ]

For 2 mol of CaC2 , 4 mol of Ca are required

[ From(ii) ]

We can represent this data in chain as below:

2 mol of NH3==> 2 mol of CaCN2=====> 2 mol of CaC2 ==> 4 mol of Ca

Hence , we can conclude that for 2 mol of NH3 ,4 mol of Ca are required

Therefore, the correct option is (D) 4 mol.