Viva Voce: Types of Reactions & Changes | Lab Manuals for Class 9 PDF Download

Q.1. Give the chemical equation to show displacement reaction.

Fe(s)+CuSO4(aq)⟶FeSO4(aq)+Cu(s)

Q.2. Why do we mb magnesium ribbon with sand paper before burning it?

Magnesium metal is reactive in nature, it forms a layer of magnesium oxide on its surface due to corrosion, hence to remove the impurities present on its surface we clean it with sand paper.

Q.3. What is your observation when you bum magnesium ribbon in air?

It catches fire, bums with dazzling white flame and forms white powdery mass of magnesium oxide.

Q.4. What type of reaction is the rusting of iron?

Rusting of iron is a chemical change showing combination reaction.

Q.5. Give two examples of decomposition reaction.

Silver bromide decomposes to form silver and bromine gas, when exposed to light.
Lead nitrate on heating decomposes to form lead oxide, nitrogen dioxide and oxygen gas.

Q.6. Give the test for H2 gas.

Take a burning matchstick near the mouth of a test tube in which hydrogen gas is released, the matchstick burns with a pop sound.

Q.7. When sodium sulphate reacts with barium chloride, white ppt. is formed. What is it due to?

When sodium sulphate reacts with barium chloride an insoluble white precipitate (ppt.) of barium sulphate is formed

Q.8. Why is burning of magnesium ribbon considered to be a chemical change?

When magnesium ribbon is burnt, it reacts with oxygen to form magnesium oxide, a completely new product with new properties.

Q.9. Give two physical properties of hydrogen gas.

It is colourless, odourless and combustible gas.

Q.10. What would happen if you place zinc metal in copper sulphate solution?

Zinc metal reacts with copper sulphate to form zinc sulphate, colourless solution and copper metal is displaced.

Q.11. Name the metal that is silver grey, brittle in nature, present in granules.

Zinc.

Q.12.  State four different types of chemical reactions.

Combination reaction, decomposition reaction, displacement reaction and double displacement reaction.

Q.13. Give the chemical equation of double displacement reaction.

Na₂SO₄(aq) + BaCl₂(aq) ⟶ BaSO₄(ppt) + 2Nacl(aq)

Q.14. What happens when crystals of copper sulphate are heated in a test tube?

The blue coloured copper sulphate crystals on heating loses water and turns white.

Q.15. What happens when copper metal is dipped in iron sulphate solution?

No change as copper is less reactive than iron and cannot displace it.

Q.16. Give one example of exothermic reaction.

Zinc + dil. sulphuric acid reaction is highly exothermic.

Q.17. What happens to the blue colour copper sulphate solution when you dip an iron nail into it?

When iron nail is dipped into blue coloured copper sulphate solution, the blue colour changed to green as iron displaces copper ions and on the surface of iron, brown colour copper metal gets deposited.

Q.18. When zinc reacts with sulphuric acid, what is formed and how do you test the same?

When zinc reacts with dilute sulphuric acid, zinc sulphate solution is formed and hydrogen gas is released, it can be tested by bringing a burning matchstick near the evolving gas which will bum with a pop sound.

Q.19. What happens to blue colour copper sulphate when zinc is added to it?

The blue colour fades and becomes colourless because zinc displaces copper ions from copper sulphate to form zinc sulphate solution.

Q.20.  Give one example/reaction which shows both physical change and chemical change.

Burning of candle
Melting of wax ⟶Physical change
Burning of wax⟶ Chemical change

Q.21. What is the colour of iron sulphate crystals?

It is green in colour

Q.22. Give one example of a chemical reaction in which precipitate is formed.

Sodium sulphate and barium chloride react together to form barium sulphate, which is white insoluble precipitate.

Q.23. Name the metal that is silvery white, present in ribbon form.

Magnesium.

Q.24.  Give two examples of combination reaction seen in daily life.

Iron reacts with oxygen to form iron oxide and copper reacts with carbonates present in air to form copper carbonate.

Q.25. Why is a chemical change called a chemical reaction?

In chemical change, two or more substances react together to form a new product with new properties, so it is called a chemical reaction.