Test: Combination And Decomposition Reaction - Class 10 MCQ

When calcium oxide (chemical formula: Ca0) reacts with water (chemical formula: H20), the following reaction takes place:

The product of this reaction is calcium hydroxide, also known as slaked lime. Thus, when calcium oxide reacts with water, slaked lime is produced. 

Slaked lime is calcium hydroxide which reacts slowly with the carbon dioxide present in air to form thin and shiny layer of calcium carbonate. The chemical reaction is:
Ca(OH)_2(aq) + CO_2(g) → CaCO_3(s) + H₂O_(l)

A chemical change must occur which is generally observed with physical changes like precipitation, heat production, color change etc. A reaction can take place between two atoms or ions or molecules and they form a new bond and no atom is destroyed or created but a new product is formed from reactants. The rate of reaction depends on and is affected by factors like pressure, temperature, the concentration of reactants.

Sulphur dioxide is a compound and oxygen is in elemental form. They combine to form sulphur trioxide.

Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule. Photodissociation is not limited to visible light.

A reaction in which two or more reactants combine together to form a single product.
Example : C + O₂ → CO₂

Combination reaction
A chemical reaction in which two or more substances combine to form a single new substance is called a combination reaction.
Representation: A + B → AB

When a magnesium ribbon is burned in air, it burns with a dazzling white flame producing white ash.

Yes, Mg is oxidized.

2Mg + O₂ → 2MgO

A Chemical Reaction is a process that occurs when two or more molecules interact to form a new product(s)

The chemical reaction that takes place when limestone is heated is
CaCo₃ → CaO + CO₂.

Electrolytic decomposition reactions are used to obtain metals from their chloride or oxide ores.

The Chemical Formula of lime water is Ca(OH)₂ (Calcium Hydroxide).