VARDAAN LEARNING INSTITUTE

Q1. On adding a drop of Barium Chloride solution to an aqueous solution of Sodium Sulphite, a white precipitate is obtained.

1. Write the balanced chemical equation of the reaction involved.
2. What other name can be given to this precipitation reaction?
3. On adding dilute Hydrochloric Acid to the reaction mixture, white precipitate disappears. Why? Write the chemical equation for this reaction.

Q2. A metal 'M' reacts with strong acid to form gas 'G'. Metal 'M' does not react with cold water or hot water but reacts with steam. Gas 'G' is flammable.

1. Identify 'M' and 'G'.
2. Write the reaction of 'M' with steam.
3. Does 'M' react with dilute HCl? If yes, write the equation.

Q3. 'X' is a metal which is used in galvanization. 'X' reacts with 'Y' (an acid) to form sulphate salt and a gas 'Z'.

1. Identify X, Y, Z.
2. Write the reaction.
3. How will you test for gas Z?

Q4. A water insoluble substance 'X' on reacting with dilute $H_2SO_4$ releases a colourless and odourless gas accompanied by brisk effervescence. When the gas is passed through water, the solution obtained turns blue litmus red. On bubbling the gas through lime water, it initially becomes milky and milkiness disappears when excess gas is passed.

1. Identify the substance 'X'.
2. Write the chemical equations for the reactions involved.

Q5. You are provided with two beakers A and B. Beaker A contains Copper Sulphate solution and Beaker B contains Iron Sulphate solution. You are given Iron nails and Copper wire. In which beaker will a reaction take place? Explain with equation.

Q6. A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.

1. Why do silver articles turn black? Name the phenomenon.
2. Name the black substance formed and give its chemical formula.

Q7. $2g$ of Ferrous Sulphate crystals are heated in a dry boiling tube.

1. List any two observations.
2. Name the type of chemical reaction taking place.
3. How many water molecules of crystallization are lost?
4. Write balanced equation.

Q8. Identify the oxidizing agent and reducing agent in the following reaction by analysing the oxidation numbers:

$3MnO_2 + 4Al \rightarrow 3Mn + 2Al_2O_3$

Explain why Aluminium is used in this process and name the process.

Q9. In the electrolysis of water:

1. Name the gas collected at the anode and cathode.
2. Why is the volume of gas collected at one electrode double that of the other?
3. What would happen if dilute $H_2SO_4$ is not added to water?

Q10. A student mixes solutions of Lead Nitrate and Potassium Iodide.

1. What is the colour of the precipitate formed? Name the compound.
2. If the student mixes solid Lead Nitrate and solid Potassium Iodide, will the reaction take place? Give reason.

Q11. Why do we store Silver Chloride in dark coloured bottles?

Case Study 1: Rancidity

Pratibha observed that the taste and smell of the fried chips left in an open packet changed after a few days. She knew this was due to rancidity.

12. What is the chemical cause of rancidity?
13. Name a gas used to flush chips packets to prevent this.
14. Name two antioxidants used in food industry.

Case Study 2: Decomposition Reactions

A decomposition reaction is a reaction in which a single reactant breaks down into two or more simpler products. It requires energy in the form of heat, light or electricity.

15. Write one equation for decomposition by Heat.
16. Write one equation for decomposition by Light.
17. Write one equation for decomposition by Electricity.