Carbon and its Compounds — Science STD 10 — Question

In terms of electronic configurations, explain the variation in the size of the atoms of the elements belonging to the same period and same group.

Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Explain why, an aqueous solution of sodium chloride is not used for the electrolytic extraction of sodium metal.

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.

A white shirt has a yellow stain of curry. When soap is rubbed on this shirt during washing, the yellow stain turns reddish-brown. On rinsing the shirt with plenty of water, the reddish-brown stain turns yellow again.

1. Name the natural indicator present in curry stain.
2. Explain the changes in colour of this indicator which take place during washing and rinsing the shirt.
3. What is the nature of soap (acidic/ basic) as shown by the indicator present in curry stain?

A colourless lead salt, when heated, produces a yellow residue and brown fumes:

1. Name the lead salt.
2. Name the brown fumes.
3. Write a chemical equation of the reaction involved.

Write any two natural and two synthetic indicators.
A student dropped few pieces of marble in dilute HCl contained in a test tube. The evolved gas was passed through lime water.

1. What change would be observed in lime water?
2. Write balanced chemical equation for the above change.

Explain the process of preparation of soap in laboratory.

List three advantages each of:

1. Exploiting resources with short term aims.
2. Using a long term perpective in managing our natural resources.