Question

20 cm pyrolusite ore exactly requires 29.2 gm HCl for complete reaction
MnO, + 4HC1 MCI, + C1, + 2H,0
The mass percent of pure MnO, in the pyrolusíte ore is (Mn = 55)
(A) 17.4%
(B) 87 %
(C) 43.5 %
(D) 14.6%​

Answer 1

Answer:

The correct answer is option B.

Explanation:

$MnO_2+ 4HCl\rightarrow MCI_2 + Cl_2 + 2H_2O$

Moles of HCl = $\frac{29.2 g}{36.5 g/mol}=0.8 mol$

According to reaction, 4 moles of HCl reacts with 1 mole of  $MnO_2$

Then, 0.8 moles of HCl; will recat with:

$\frac{1}{4}\times 0.8 = 0.2 mol$ of $MnO_2$

Mass of 0.2 moles of $MnO_2$:

0.2 mol × (55 g/mol+ 2 × 16 g/mol)= 17.4 g

The mass percent of pure $MnO_2$ in the pyrolusíte ore is :

$\frac{17.4 g}{20 gm}\times 100=87\%$