NTSE Level Test: Chemical Reactions & Equations - Class 10 MCQ

“The statement that substances appearing on the left hand side of the equation are called products” is incorrect.

Iodine is purple in colour.

The balanced equation for the reaction is
3Fe + 4H₂O → Fe₃O₄ + 4H₂

In the reaction MnO2 + 4HCl -> MnCl2 + Cl2 + 2H2O , Cl (chlorine) is the substance which is oxidized from the HCl, and it is the reducing agent for the MnO2 as well. As Cl is the oxidized substance in HCl, thus it is the oxidizing agent in the reaction.

The calcium hydroxide used for white washing the walls reacts with the carbon dioxide (CO₂) present in the air to form Calcium carbonate (CaCO₃) which gives shiny appearance to the walls.
The chemical reaction occurring during the conversion of slaked lime (calcium hydroxide) to calcium carbonate which gives the shiny appearance to the walls is as follows:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Zn + 2AgNO₃→ Zn(NO₃)₂ + 2Ag

The reaction takes place as under

2Cu(NO₃)₂   2CuO + 4NO₂ + O₂

Heat is evolved only when water reacts with quick lime and when the acid is diluted with water.

As we know, H₂ and O₂ are present in the form of gas in atmosphere and H₂O as liquid.

4NH₃ (g) + 5O₂(g) → 4NO(g) + 6H₂O(g) is an example of displacement as well as redox reaction. Oxygen displaces hydrogen of ammonia. Hence, this is a displacement reaction. Nitrogen of ammonia is getting oxidized with the addition of oxygen. This is also an example of redox reaction. 

BaCl_2​ + (NH₄​)₂​SO₄​ →  BaSO₄​ + 2NH₄​Cl        
Above reaction is a double displacement reaction as ions (both cations and anions) of the reacting molecules are exchanged. Barium ion (Ba²⁺) combines with sulphate ion (SO₄²⁻​) to form Barium sulphate (BaSO⁴​) and ammonium ion (NH⁴⁺​) combines with chloride ion(Cl⁻) ion to form ammonium chloride(NH₄​Cl).
The above reaction is also classified as a precipitation reaction because barium and sulphate ions combine to form precipitates of barium sulphate.
Ba²⁺ + SO₄²⁻​→ BaSO₄​(s)

Heat is absorbed when dry ice sublimes and water evaporates. Therefore, cooling is produced.

Clearly, It is a decomposition reaction and it requires heat to get decomposed into KCl and O₂.

Quick lime(CaO) combines with water to form calcium hydroxide (Ca(OH)₂). It is an exothermic reaction as heat is produced in the reaction.  
CaO + H₂O → Ca(OH)₂ + heat
On  adding excess of calcium hydroxide in water, a saturated solution of calcium hydroxide is formed which is called lime water. Lime water is basic in nature and therefore has a pH above 7.

Nitrogen or helium can be used for storage of fresh sample of oil for long time. Helium and Nitrogen both the gases provide inert atmosphere.

The anions and cations are exchanged in the reaction (ii) only.

The water decomposes during electrolysis to form hydrogen and oxygen gases in the ratio 2:1 by volume.

For an exothermic reaction, heat releases during reaction so temperature increases whereas endothermic reactions proceed with absorption of heat which decrease the temperature of reaction.

Copper wire on heating in presence of air at high temperature forms copper oxide, which is a chemical reaction. Processes in (a), (b) and (c) do not involve any chemical change.