English Medium कक्षा १० - CBSE Important Questions for Science

Solve the following question:
In an electric circuit, two resistors of 12 0 each are joined in parallel to a 6 V battery. Find the current drawn from the battery.

An electric motor rated 1100 W is connected to 220 V mains. Find: 

1. The current drawn from the mains,
2. Electric energy consumed if the motor is used for 5 hours daily for 6 days.
3. Total cost of energy consumed if the rate of one unit is 5.

Let the resistance of an electrical device remain constant, while the potential difference across its two ends decreases to one fourth of its initial value. What change will occur in the current through it? State the law which helps us in solving the above stated question. 

Write two methods of preventing the rusting of iron.

\[\ce{Fe2O3 + 2Al -> Al2O3 + 2Fe}\]

The above reaction is an example of a ______.

Translate the following statement into a chemical equation and then balance it.

Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.

Translate the following statement into a chemical equation and then balance it.

Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

Write the balanced chemical equation for the following reaction.

\[\ce{Aluminium + Copper chloride -> Aluminium chloride + Copper}\]

Write the balanced chemical equation for the following reaction.

\[\ce{Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water}\]

Write the balanced chemical equation for the following and identify the type of reaction. 

\[\ce{Potassium bromide (aq) + Barium iodide (aq) -> Potassium iodide (aq) + Barium bromide (s)}\]

What do you mean by a precipitation reaction? Explain giving an example.

Give reasons:

Platinum, gold and silver are used to make jewellery.

On what basis is a chemical equation balanced?

Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.

What is meant by a decomposition reaction?

Complete the following equation:
CH₄ + O₂ —>

Complete the following equation:

CH₂ + H₅OH `("Hot Conc." H_2SO_4)/`>

Complete the following equation:

CH₃COOH + NaOH → 

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 them again, and recorded that as ‘y’. The percentage of water absorbed by raisins may be determined using the relationship.

In the experiment for determining the percentage of water absorbed by raisins, we do the final weighing of the raisins after keeping them dipped in water for about one hour. For the accuracy of the result, the extra water from the surface of the soaked raisins is removed by