Chemical Reactions and Equations — Science STD 10 — Question

Fresh milk has a pH of 6. When milk changes into curd, the pH value will:

1. Become 7
2. Become less than 6
3. Become more than 7
4. Remain unchanged.

One of the following is an exothermic reaction. This is:

The salt which will give an acidic solution on dissolving in water is:

1. KCl
2. NH₄Cl
3. Na₂CO
4. CH₃COONa

To protect tooth decay we are advised to brush our teeth regularly. The nature of the tooth paste commonly used is:

1. Acidic.
2. Neutral.
3. Basic.
4. Corrosive.

A student puts one big iron nail each in four test tubes containing solutions of zinc sulphate, aluminium sulphate, copper sulphate and iron sulphate. A reddish brown coating was observed only on the surface of iron nail which was put in the solution of:

Baking soda is a mixture of :

Washing soda is a

A student weighed some raisins and recorded the weight as ‘x’. She then soaked the raisins in distilled water. After about 2 hours she removed the raisins, wiped them dry and weighed again and recorded that as ‘y’. The percentage of water absorbed by raisins may be determined using the relationship:

A solution reacts with marble chips to produce a gas which turns lime water milky. The solution contains:

1. Na₂SO₄
2. CaSO₄
3. H₂SO₄
4. K₂SO₄

A student takes about 6 ml of distilled water in each of the four test tubes P, Q, R and S, then dissolves an equal amount of four different salts namely sodium chloride in ‘P', potassium chloride in ‘Q', calcium chloride in ‘R' Cand magnesium chloride in ‘S'. He then adds 10 drops of soap solution to each test tube and shakes its contents. The test tubes in which scum (insoluble substance) is formed with soap are: