21.

Which is the best reagent to distinguish between propene and propyne ?

• ammonical AgNO₃

• $\frac{{\mathrm{Br}}_2}{{\mathrm{CCl}}_4}$

• alkaline KMnO₄

• aqueous Br₂

The octane number of a sample of petrol is 40 .It means that its knocking property is equal to the mixture of :

• 40% n-heptane + 60% iso-octane

• 40% petrol + 60% iso-octane

• 60% n-heptane + 40% iso-octane

• 60% petrol + 40% iso-octane

The main component of marshgas is :

• methane

• ethane

• butane

• isobutane

The ratio of Fe₂O₃ and Al, in thermite is :

• 1 : 3

• 1 : 2

• 3 : 1

• none of these

Which of the following reaction is a redox reaction ?

• P₂O₅ + 2H₂O $\to$ H₄P₂O₇

• 2AgNO₃ + BaCl₂ $\to$ 2AgCl + Ba(NO₃)₂

• BaCl₂ + H₂SO₄ $\to$ BaSO₄ + 2HCl

• Cu + 2AgNO₃ $\to$ Cu(NO₃)₂ + 2Ag

What is 'A' in the following reaction ?

2Fe³⁺(aq) + Sn²⁺(aq) $\mathrm{\to }$ 2Fe²⁺(aq) + A

• Sn³⁺(aq)

• Sn⁴⁺(aq)

• Sn²⁺(aq)

• Sn

The following four solutions are kept in separate beakers and copper metal is put in each of them. Which solution will become blue after some time ?

• AgNO₃ solution

• Zn(NO₃)₂ solution

• Ba(NO₃)₂ solution

• NaNO₃ solution

The molecular formula of 'salt petre' is :

• KNO₃

• NaNO₃

• NaCl

• Na₂SO₄

Which equation is correct for first order reactions ?

• t_1/2 $\propto$ C^-1

• t_1/2 $\propto$ C

• t_1/2 $\propto$ C^o

• t_1/2 $\propto$ C^1/2

87.5% decomposition of a radioactive substance complete in 3 hours. What is the half-life of that substance ?

• 2 hours

• 3 hours

• 90 minutes

• 1 hour