Chemical reactions and equations class 10 questions Answers

Chemical reactions and equations class 10 questions Answers

Chemical reactions and equations class 10 questions Answers are for students of class 10 who come under the class 10 cbse board. With the class 10 science syllabus being vast covering topics like the Periodic classification of elements, Carbon compounds, Metals and non-metals, Acids, bases and salts, and more, it is important that a student must learn all the important questions and topics which usually tend to repeat through the years in the university papers. That is why here we have provided Chemical reactions and equations class 10 questions Answers so that students can effectively improve their learning and give out a better effort for the cbse board exam.

1. What is electrolytic decomposition? (2 marks)

Ans: The process of decomposition of any molecule using electricity is termed as electrolytic decomposition. The application of this is when we need to separate molecules which dissociate at high temperatures. One such case would be sodium chloride. Sodium Chloride dissociates at high temp but breaks apart easily on electrolytic decomposition.

2. Give two uses of quicklime. (2 marks)

Ans: Quicklime also known as calcium oxide has multiple applications. Two of them are:

Quicklime is used extensively in the process of creating cement.

Lime is used as a reagent in laboratories for dehydration, precipitation, etc.

3. What is the difference between single displacement and double displacement reactions with the help of suitable examples to help solve the same (3 marks)

Ans: A single displacement reaction is a reaction in which the one or more elements replaces another element in a compound. Whereas in a double displacement reaction, there are two exchanges of ions between compounds resulting in two new compounds.

Consider 4 elements A, B, C & D. In a single displacement reaction, the mechanism would be as follows.

AB + C -> AC + B

Wherein C & B are pure elements and are exchanged forming 2 compounds with A.

Considering the case of a double displacement reaction:

AB + CD -> AC + BD

4. Why are oil and fat containing food items flushed with nitrogen? (3 marks)

Ans: Nitrogen is an inert gas and thus does not react with fats and oils present in food substances. But the case with oxygen is different as it makes food rancid by reacting it with food items. Thus packing oil and fatty foods with nitrogen and fatty foods will help to sustain the quality of the food for longer by removing the oxygen before packing.

5. How do we balance a chemical equation? (4 marks)

Ans: Balancing a chemical reaction is mandatory and required to understand the ratios involved in the action of a chemical reaction. There are several steps which need to be noted when balancing a chemical reaction, let us look at them one by one.

First, write the unbalanced chemical reaction. If the unbalanced chemical reaction is not given, use the components of the chemical reaction that are mentioned and write down the skeletal equation.

Now take note of how many atoms are on each side of the reaction of each element. The subscript of an element represents the rate of the number of atoms. If the number of atoms on the reactant side is not equal to the number of atoms on the product side, then we can confirm that the equation is not balanced. This contradicts the law of conservation of mass, thus we must balance the chemical reaction.

Add coefficients to the compounds or elements in the chemical reaction so that the number of atoms on both sides of the reaction matches up for all the constituent elements.

Keep notice to balance oxygen and hydrogen atoms last as they are present in a variety of compounds and trying to fix that ratio first will complicate things further.

Check out this page to learn further in detail: Balancing Chemical Equations

6. Explain four different types of chemical reaction with suitable examples. (8 marks)

Redox reaction: A REDuction-OXidation reaction is a reaction in which there is a transfer of electrons between chemical species. Let us consider the example of an electrochemical cell-like redox reaction between Zinc and Hydrogen.


Here, A Zinc atom reacts with 2 ions of positively charged hydrogen to which electrons get transferred from zinc atom and hydrogen becomes a stable molecule and Zinc ion is the product.

Neutralization reaction: It is basically the reaction between an acid and a base giving salt and water as the products. The water molecule formed is by the combination of OH– ions and H+ ions. The overall pH of the products when a strong acid and a strong base undergo a neutralization reaction will be 7. Consider the example of the neutralization reaction between Hydrochloric acid and Sodium Hydroxide giving out sodium chloride(Common Salt) and water.


Here, an acid and a base, Hydrochloric acid and Sodium Hydroxide react in a neutralization reaction to produce Sodium Chloride(Common Salt) and Water as the products.

Decomposition reaction: A Decomposition reaction is a reaction in which a single component breaks down into multiple products. Certain changes in energy in the environment have to be made of heat, light or electricity breaking bonds of the compound. Consider the example of the decomposition of calcium carbonate giving out CaO (Quick Lime) which is a major component of cement.

CaCO3(s)→Heat CaO(s)+CO2(g)

Here, the compound Calcium carbonate when heated breaks down into Calcium Oxide and Carbon Dioxide.

Combustion reaction: A combustion reaction is a reaction with a combustible material with an oxidizer to give an oxidized product. An oxidizer is a chemical a fuel requires to burn, generally oxygen. Consider the example of combustion of magnesium metal.


Here, 2 magnesium atoms react with a molecule of oxygen producing 2 molecules of the compound magnesium oxide releasing some heat in the process.

7. How is exothermic reaction different from an endothermic reaction? (3 marks)

Ans:An exothermic reaction is a reaction in which there is an expulsion of energy which can be in the form of light or heat. Whereas an endothermic reaction is one in which the system absorbs heat from the surroundings mostly in the form of heat energy. Examples of an exothermic reaction are Rusting iron, settling, chemical bonds, explosions, nuclear fission whereas some examples of an endothermic reaction are Melting ice, evaporation, cooking, gas molecules, photosynthesis.

8. Explain the process of corrosion and rusting. (2 marks)

Ans:Corrosion is the natural process by which a naturally pure metal converts into a more stable form of itself like sulfide, hydroxide or oxide. It is an actual degradation of the metal as it renders the metal useless of its usual metallic character.

Rusting is the specific name given to the corrosion of iron. Rust can be termed with the chemical formula of Iron Oxide with its general form formula being Fe2O3. N H2O. Iron when in contact with air moisture or water, corrodes and forms rust.

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