Metals and Non-Metals — Science STD 10 — Question

A milkman adds a very small amount of baking soda to fresh milk.

1. Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
2. Why does this milk take a long time to set as curd?

What happens when an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride? State the physical conditions of reactants in which the reaction between them will not take place. Write the balanced chemical equation for the reaction and name the type of reaction.

Give the general formula of an:

1. Alkane.
2. Alkene.
3. Alkyne.

Give account of chemical properties?
Dehydration of C₂H₅OH.

A gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.

Identify the substances that are oxidised and the substances that are reduced in the following reactions.

1. 4Na(s) + O₂(g) → 2Na₂O(s)
2. CuO(s) + H₂(g) → Cu(s) + H₂O(l)

A person found that the cake prepared by him is hard and small in size. Which ingredient has he forgotten to add that would have caused the cake to rise and become light? Explain your answer.

Which of the two is better for washing clothes when the water is hard: soap or detergent? Give reason for your answer.

Which of the following hydrocarbons will give substitution reactions and why?
CH_4, C₃H₆, C₃H₈, C₄H₆, C₅H₁₂, C₅H₁₀.

State how the valency of elements varies.

1. In a group.
2. In a period, of the periodic table.