Class 10 Science Chapter 1 MCQ

A combination reaction is one in which or more reactants combine to form a single product. MgO and H2O combine to from Mg (OH)2. 4Al and 3O2 combine to form Al2O3. A combination reaction is also known as synthesis reaction. Hence, your answer will be option [D].

It is because, the standard state for hydrogen and oxygen is gas and for water is liquid at reaction temperature.

During a chemical reaction the chemical composition of a substance changes. A chemical reaction produces a new substance with new properties. Energy is either released or absorbed during a chemical reaction. It is an irreversible reaction. You can easily understand by this equation: 2CU (copper wire) + O2 → 2CuO (copper oxide)

Lead sulphate being insoluble will not dissociate into Pb2+ ions.

In a decomposition reaction, a compound is broken down into two or more simpler substances. This reaction is a decomposition reaction as KClO3 is broken down into KCl and O2. It is also endothermic reaction because during decomposition of KCIO3 heat is taken in for the formation of desired products.

Helium or nitrogen both can be used for storage of fresh sample of an oil for a long time. These gases are called inert gases as they do not react with most elements including oxygen. Thus, these gases create an inert environment for the oil and prevent its reaction with any element in the environment that prevent from getting it stale.

According to the law of conservation of mass, matter can neither be created nor destroyed in a chemical reaction. This means that the total mass of all reactants must be equal to the total mass of the products. In other words, we can say that the number of various types of atoms in reactants must be equal to the number of same type of atoms in products.

Lead acetate can be used in place of lead nitrate because lead acetate is also water soluble like lead nitrate. You can easily understand by this equation: Pb(CH3 COO)2 + 2Kl → Pbl2 + 2CH3COOK (Lead acetate) Lead iodide(Yellow ppt) When potassium iodide and lead acetate are mixed, a bright yellow precipitate of lead iodide is seen. Lead iodide is unusually soluble in hot water and forms crystals on cooling.

Sublimation of dry ice and evaporation of water both are endothermic processes. These processes pull heat (energy) from their surroundings to change from one state to another. Hence both these processes produce cooling rather than heating. Dry ice absorbs heat from the environment to convert into gas.

The chemical reaction between barium hydroxide and ammonium chloride to form barium chloride, ammonia and water is characterized by a change in temperature. (Here, is a fall in temperature.)

Here are all the statements are correct. Hence, your answer will be option [D].

This reaction is a double displacement reaction as well as a precipitation reaction. This is a double displacement reaction because one component of each compound has exchanged places with each other. It is also called a precipitation reaction due to the formation of white precipitate of barium sulphate. Rest other products formed are soluble in water except barium sulphate that precipitates out.

A precipitate is a “Solid product” which separate out from the solution during a chemical reaction.

Slaking of lime is an exothermic reaction because a large amount heat is produced during the reaction. The heat can be felt by touching the beaker from outside. The resulting compound Ca(OH)2, which is also called slaked lime, turns red litmus solution to blue and hence proves it to be a basic solution. Thus, the pH of this solution will be more than seven. You can easily understand by this equation: CaO + H2O → Ca(OH)2 + Heat

Carbon dioxide gas is evolved when dilute hydrochloric acid is poured over sodium carbonate.

Here are all the statements are correct. Hence, your answer will be option [D].

Double displacement reactions are such chemical reactions in which one component of each reactant exchange to form products. The cations and anions of two compounds exchange their ions to form two new compounds. Here only in reaction (B), ions of both reactants are exchanged and two entirely different compounds are formed.

KMnO4 is an oxidising agent, it oxidises FeSO4. You can easily understand by this equation: 2KMnO4 + 8H2SO4 + 10 FeSO4 → K2SO4 + 5Fe2(SO4)3 + 2MnSO4 + 8H2O

Here are all the statements are correct. Hence, your answer will be option [D].

Chemical reaction in beakers A and B gives out heat. Hence, the temperature of the solution increases. We can call it an exothermic reaction. In beaker C, heat is absorbed from water instead and hence the temperature decreases. Now, we can call it an endothermic process.

When quick lime reacts with water, calcium hydroxide is produced and a large amount of heat is released. Similarly, when an acid or a base is diluted with water, heat is released making it a highly exothermic reaction.

Here are all the statements are correct. Hence, your answer will be option [D].

Iron is getting oxidized and forming ferrous ferric oxide (Fe3O4)4. Water molecule is getting reduced to hydrogen ions. Water is acting as an oxidizing agent by donating its oxygen atom to Fe.

This is a redox reaction because oxidation and reduction both are happening simultaneously. It is also a displacement reaction because H of NH3 is displaced by oxygen. A displacement reaction is also a redox reaction as it is always followed by oxidation as well as reduction. Note: When oxygen is added to a compound in a reaction, it is called oxidation. Removal of oxygen from a substance during a reaction is called reduction.

Combustion of Liquefied Petroleum Gas (LPG) is not a physical change. It is a chemical change because combustion of LPG produces new substances. A lot of heat is produced along with carbon dioxide and water vapour during this reaction. It is also irreversible in nature. Rest three are physical changes as no new products are formed; the only state of the substance changes. Hence, your answer will be option [D].