Combination Reaction

Q.

When magnesium ribbon is burnt in air, then identify the type of reaction and colour of ash formed.

1. Colour of ash formed:- Black

   Type of reaction:- Decomposition

2. Colour of ash formed:- White

   Type of reaction:- Decomposition

3. Colour of ash formed:- Yellow

   Type of reaction:- Decomposition

4. Colour of ash formed:- White

   Type of reaction:- Combination

Q. Arrange the given metals in the decreasing order of their reactivity.
Aluminium, sodium, gold, copper, and iron.

Q.

Which of the following are combination reactions?

(i)$2{\mathrm{KClO}}_3\stackrel{\mathrm{heat}}{\to }2\mathrm{KCl}+3{\mathrm{O}}_2$

(ii) $\mathrm{MgO}+{\mathrm{H}}_2\mathrm{O}⟶\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$

(iii) $4\mathrm{Al}+3{\mathrm{O}}_2⟶2{\mathrm{Al}}_2{\mathrm{O}}_3$

(iv) $\mathrm{Zn}+{\mathrm{FeSO}}_4⟶{\mathrm{ZnSO}}_4+\mathrm{Fe}$

1. (i) and (iii)

2. (iii) and (iv)

3. (ii) and (iv)

4. (ii) and (iii)

Q.

The least reactive metal among the following is :

1. Sodium
2. silver
3. copper
4. lead

Q. When lead nitrate is heated, a reddish-brown coloured gas is liberated. Name the gas.

1. Nitrous oxide
2. Nitrogen pentoxide
3. Nitric oxide
4. Nitrogen dioxide

Q.

What type of reaction would you classify burning of coal as?

1. Decomposition Reaction

2. Combination Reaction

3. Double Displacement Reaction

4. Single displacement Reaction

Q.

Fill in the blanks :

(a) A reaction in which two or more substances combine to form a single substance is called a ___ reaction.

(b) A ___ is a substance which changes the rate of a chemical reaction without undergoing a chemical change.

(c) The formation of gas bubbles in a liquid during a reaction is called___

(d) The reaction between an acid and a base is called ___

(e) Soluble bases are called ___

(f) The chemical change involving iron and hydrochloric acid illustrates a ___ reaction.

(g) In the type of reaction called ___ two compounds exchange their positive and negative radicals respectively.

(h) A catalyst either ___ or ___ the rate of a chemical change but itself remains ___ at the end of the reaction.

(i) The chemical reaction between hydogen and chlorine is a ___ reaction

(j) When a piece of copper is added to silver nitrate solutuions, it turns ___ in colour.

Q. $\text{A+B}\to \text{AB}$ is an example of reaction.

1. combination
2. decomposition
3. double decomposition

Q. Which of the following metals can displace the other two metals from their salt solutions? [2 marks]
zinc, iron, copper

Q.

Why we can’t make water by adding 2 molecules of hydrogen and a molecule of oxygen?

Q. Which of the following is/are example(s) of combination reaction?

1. ${\text{CH}}_4+2{\text{O}}_2\to {\text{CO}}_2+2{\text{H}}_2\text{O}$
2. $\text{MgO}+{\text{CO}}_2\to {\text{MgCO}}_3$
3. $\text{CaO}+{\text{O}}_2\to 2{\text{CaCO}}_3$
4. $2\text{AgCl}+\stackrel{\text{sunlight}}{⟶}2\text{Ag}+{\text{Cl}}_2$

Q.

A reaction in which a single product is formed from two or more reactants is known as:-

1. decomposition reaction

2. combination reaction

3. displacement reaction

4. double displacement

Q.

Tyndall effect is observed when light passes through:

1. Copper sulphate solution

2. Sodium chloride solution

3. Water

4. Starch solution

Q.

$CaO\left(s\right)+H_{2}O\left(l\right)\to Ca\left(OH{)}_2\right(aq)+heat$

What can be inferred from the above reaction?

(i) $CaO$ is solid.

(ii) $CaO$ reacts with water.

(iii) $H_{2}O$ is liquid.

(iv) $H_{2}O$ is in vapour state.

(v) $Ca(OH{)}_2$ forms a solution with water.

(vi) The reaction is exothermic.

1. (i), (iii), (iv), (vi)

2. (i), (ii), (iii), (v), (vi)

3. (ii), (iii), (v), (iv)

4. (v), (iv)

Q. Iron is less reactive than _____.

1. Silver
2. Copper
3. Magnesium
4. Gold

Q.

A shiny brown coloured element $X$ on heating in the air becomes black in colour to form compound $Y$. Name the element $X$, the black coloured compound $Y$ and identify the type of the reaction.

1. X:- Copper

   Y:- Copper dioxide

   Type of reaction:- Combination reaction

2. X:- Sodium

   Y:- Sodium Oxide

   Type of reaction:- Combination reaction

3. X:- Copper

   Y:- Copper oxide

   Type of reaction:- Combination reaction

4. X:- Sodium

   Y:- Sodium Dioxide

   Type of reaction:- Combination reaction

Q. Formation of water from hydrogen and oxygen is an example of _________ reaction.

1. combination
2. decomposition
3. displacement
4. precipitation

Q.

What is a combination reaction? Explain with an example.

Q.

Identify the types of reactions:-

(i) $H_2\left(g\right)+C{l}_2\left(g\right)\to 2HCl\left(g\right)$

(ii) $NaOH\left(aq\right)+HCl\left(aq\right)\to NaCl\left(aq\right)+H_{2}O\left(l\right)$

(iii) $Fe\left(s\right)+S\left(s\right)\stackrel{heat}{\to }FeS\left(s\right)$

1. (i) Displacement reaction

   (ii) Double Displacement reaction

   (iii) Combination reaction

2. (i) Neutralisation reaction

   (ii) Double Displacement reaction

   (iii) Combination reaction

3. (i) Combination reaction

   (ii) Double Displacement reaction

   (iii) Endothermic and combination reaction

4. (i) Exothermic and combination reaction

   (ii) Double Displacement reaction

   (iii) Combination reaction

Q. Arrange the given metals in the decreasing order of their reactivity.
Aluminium, sodium, gold, copper, and iron.

Q. What type of chemical reaction takes place when i) limestone is heated?
ii) a magnesium ribbon is burnt in air?

Q. Give balanced chemical equation for the reaction of water with
$\left(c\right)$ Carbon dioxide

Q.

What is exothermic and an endothermic reaction?
Amongst the following reactions, identify the exothermic reaction and the endothermic reaction:
1. Heating coal in air to form carbon dioxide.
2. Heating limestone in lime kiln to form quick lime. [3 MARKS]

Q. Identify the examples of combination reaction from the options given below.

1. $\text{Fe(s)}+{\text{CuSO}}_4\text{(aq)}\to {\text{FeSO}}_4\text{(aq)}+\text{Cu(s)}$
2. $8\text{Fe(s)}+{\text{S}}_8\text{(s)}\to 8\text{FeS(s)}$
3. $\text{MgO(s)}+{\text{CO}}_2\text{(g)}\to {\text{MgCO}}_3\text{(s)}$
4. $3{\text{Pb(NO}}_3{)}_2\text{(aq)}+2{\text{AlCl}}_3\text{(aq)}$ $\to$ $3{\text{PbCl}}_2\text{(s)}\downarrow +2\text{Al}{\text{(NO}}_3{)}_3\text{(aq)}$

Q. What ia an endothermic reaction?

Q. Write combination reaction and decomposition reaction with one example each.

Q. Iron is less reactive than _____.

1. Silver
2. Copper
3. Magnesium
4. Gold

Q. How chemical displacement reactions differ from chemical decomposition reaction? Explain with an example for each.

Q.

Metal Reactivity series is the arranged list of metals based on their reactivity.

1. True

2. False

Q. What are combination reactions?