# Worksheet 1: Chemical Equations and Reactions

1 Mark Questions

Q1. Identify the type of reaction given below: $Fe(s)\quad +\quad CuS{ O }_{ 4 }(aq)\longrightarrow \quad FeS{ O }_{ 4 }(aq)\quad +\quad Cu(s)$

Q2. Name the brown coloured gas evolved when lead nitrate crystals are heated in a dry test tube.

Q3. Identify the substance oxidised and reduced in the reaction: $CuO(s)\quad +\quad Zn(s)\longrightarrow \quad ZnO(s)\quad +\quad Cu(s)$

Q4. Identify the reducing agent in the following reaction. $F{ e }_{ 2 }{ O }_{ 3 }\quad +\quad 3CO\quad \longrightarrow \quad 2Fe\quad +\quad 3C{ O }_{ 2 }$

2 Mark Questions

Q5. Write the balanced chemical equation for the following reactions.

(i) Silver bromide on exposure to sunlight decomposes into silver and bromine.

(ii) Sodium metal reacts with water to form sodium hydroxide and hydrogen gas.

Q6. A white salt of lead on heating decomposes to give brown fumes and a residue is left behind

(i) Name the salt

(ii) Write the equation for the decomposition reaction.

Q7. Aluminium is a reactive metal but is still used for packing food articles. Why?

3 Mark Questions

Q8. What happens when a piece of

(i) Zinc metal is added to copper sulphate solution?

(ii) Aluminium metal is added to dilute hydrochloric acid?

(iii) Silver metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs.

Q9. State the type of chemical reaction with chemical equations that take place in the following.

(i) Magnesium wire is burnt in air.

(ii) Electric current is passed through water.

(iii) Ammonia and hydrogen chloride gases are mixed.

Q10. State reason for the following

(i) Small amount of acid is added to water during electrolysis of water.

(ii) When ammonium chloride is dissolved in water in a test tube, the test tube becomes cold.

(iii) Paint is applied on iron particles.

5 Mark Questions

Q11. (i) Identify the type of reactions taking place in each of the following cases and write the balanced chemical equations for the reactions.

(a) Barium chloride solution is mixed, with copper sulphate solution and a white precipitate is obtained.

(b) On heating copper powder in air, the surface of the copper powder turns black.

(ii) What happens when hydrogen gas is passed over the heated copper oxide? Write the chemical equation involved in this reaction.

Q12. Define rancidity. What kind of substances are used to prevent rancidity? Explain any three methods to prevent rancidity.

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