List of top Science Questions on Chemical Reactions asked in CBSE Class X

Name and explain the process used to obtain sodium hydroxide from the aqueous solution of sodium chloride (Brine). Name the two gases which are given at the anode and the cathode respectively. List two uses of each of these gases.

Consider the following chemical equation:
$p \, \text{MnO}_2 + q \, \text{Al} \rightarrow r \, \text{Mn} + s \, \text{Al}_2\text{O}_3$
To balance this chemical equation, the values of the coefficients $p$, $q$, $r$, and $s$ must be respectively:

When magnesium ribbon is burnt in air, an ash of white colour is produced. Write chemical equation for the reaction giving the chemical name of the ash produced. State the type of chemical reaction giving justification for your answer.

Consider the following Chemical equation: a Al₂O₃ + b HCl → c AlCl₃ + d H₂O
In order to balance this chemical equation, the values of a, b, c and d must be

Which one of the following reactions is different from the remaining three?

Identify the product ‘X’ obtained in the following chemical reaction:

Copper powder is taken in a china dish and heated over a burner.Name the product formed and state its colour. Write the chemical equation for the reaction involved.

Write chemical equation for the chemical reaction which occurs when the aqueous solutions of barium chloride and sodium sulphate react together. Write the symbols of the ions present in the compound precipitated in the reaction.

Is the reaction exothermic or endothermic?

Assertion (A): Some vegetable oils are healthy. Reason (R): Vegetable oils generally have long unsaturated carbon chains.

To balance the chemical equation, the values of the coefficients x, y, z, and t must be: Zn(NO₃)₂ → ZnO + NO₂ + O₂

It is observed that Calcium on reaction with water floats on its surface. Explain why it happens. Also write a balanced chemical equation for the reaction that occurs. What happens when the aqueous solution of the product of this reaction reacts with Carbon dioxide gas? Write a balanced chemical equation for the reaction.

(a) “No precipitation reaction can occur without exchange of ions between the two reactants.” Justify this statement giving a balanced chemical equation for the reaction.
OR
(b) Giving one example of each, differentiate between a displacement reaction and a double displacement reaction.

Solid Calcium oxide reacts vigorously with water to form Calcium hydroxide accompanied by the liberation of heat. From the information given above it may be concluded that this reaction

Select from the following a process in which a combination reaction is involved:

Name the type of chemical reaction in which calcium oxide reacts with water. Justify your answer by giving balanced chemical equation for the chemical reaction.

Write one chemical equation each for the chemical reaction in which the following have taken place:
(i) Change in colour
(ii) Change in temperature
(iii) Formation of precipitate
Mention colour change/temperature change (rise/fall)/compound precipitated along with equation.

Assertion (A) : Hydrogen gas is not evolved when zinc reacts with nitric acid.
Reason (R) : Nitric acid oxidises the hydrogen gas produced to water and itself gets reduced.

Select from the following a decomposition reaction in which the source of energy for decomposition is light:

When 2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc in a test tube and then warmed, the reaction that occurs can be written in the form of a balanced chemical equation as: