Which of the following is a physical change?

A. The bubbling of chlorine into water

B. The bubbling of chlorine into a jar contanining hydrogen

C. The dissolution of sodium chloride in water

D. The passing of steam over heated iron

In a reaction: \(SnO_{2} + 2C → Sn + 2CO\) the mass of coke containing 80% carbon required to reduce 0.302 kg of pure tin oxide is?
(Sn - 119, O - 16, C - 12).

A. 0.40 kg

B. 0.20 kg

C. 0.06 kg

D. 0.04 kg

Cr₂O₇ + 6Fe²⁺ + 14H⁺ → 2Cr³⁺ +6Fe³⁺ + 7H₂O. In the above , the oxidation number of chromium changed from?

A. +7 to +3

B. +6 to +3

C. +5 to +3

D. -2 to +3

In the reaction 1O^-₃ + 5l^- + 6H⁺ → 31₂ + 3H₂O, the oxidizing agent is?

A. H⁺

B. l^-

C. 1O^-

D. l₂

Fe\(_2\)O\(_{3(s)}\) + 2Al\(_{(s)}\) → Al\(_2\)O\(_3\) + 2Fe\(_{(s)}\). If the heats of formation of Al\(_2\)O\(_3\) and Fe\(_2\)O\(_3\) are - 1670 kJmol\(^{-1}\) and - 822 kJmol\(^{-1}\) respectively, the enthalpy change in kJ for the reaction is ?

A. +2492

B. +848

C. -848

D. -2492

Iron galvanized with zinc is cathodically protected from corrosion. This is because?

A. zinc has a more positive oxidation potential than iron

B. zinc has less positive oxidation potential than iron

C. bith have the same oxidation potential

D. zinc is harder than iron

Which of the following samples will react fastest with dilute trioxonitrate (V) acid?

A. 5 g of lumps of CacO₃ at 25°C

B. 5 g of powered CacO₃ at 25°

C. 5 g of lumps of CaCO₃ at 50°C

D. 5 g of powered CaCO₃ AT 50°C

In the reaction:
2Hl_(g) ↔ H_2(g) + l_2(g)' ΔH = 10 kj;

The concentration of iodine in the equilibrium mixture can be increased by?

A. raising the pressure

B. raising the temperature

C. adding a catalyst

D. lowering the pressure

Which of the following gases can be collected by the upward displacement of air?

A. NO

B. H ₂

C. NH₃

D. Cl ₂

The brown fumes given off when trioxonitrate (V) acid is heated consist of ?

A. NO₂ and O₂

B. H₂O and NO₂

C. NO_2' O₂ and H₂O

D. NO, NO₂ and H₂O