Chem mc

1. Look at the chemical equation first:

2CO (g) + O2 (g) → 2CO2 (g)

So, molar ratio of CO : O2 = 2 : 1

Therefore, O2 is in excess.

So, volume of oxygen left behind (unreacted)

= 50 X 1/2

= 25 cm³

From the equation, volume of carbon dioxide produced

= no. of mole of carbon monoxide

= 50 cm³

So, final gaseous volume at the end

= volume of carbon dioxide + volume of oxygen unreacted

= 50 + 25

= 75 cm³

Therefore, the answer is B. 75 cm³.




Concentrated hydrochloric acid is not an oxidzing agent. Instead, it is a reducing agent. When concentrated hydrochloric acid is added to acidify potassium permanganate solution (which is a strong oxidizing agent in acidic medium), they will react with each other. This is a redox reaction as oxidation and reduction occur.

MnO4- (aq) + 8H+ (aq) + 5e- → Mn2+ (aq) + 4H2O (l)
Cl- (aq) → Cl2 (g) + 2e-
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2MnO4- (aq) + 5Cl- (aq) + 16H+ (aq) → 2Mn2+ (aq) + 5Cl2 (g) + 8H2O (l)

From the above, a redox reaction occurs. permanganate ions are reduced to manganese (II) ions. And chloride ions are oxidized to chlorine gas.

Observations:

a. Some greenish-yellow gas with pungent smell is evolved.

b. The colour of the solution turns from purple to colourless.