# AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS QUESTIONS ANSWERS SOLUTIONS

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- Published: 2024-06-16T21:08:46+05:30
- Author: Venkat

# AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS QUESTIONS ANSWERS SOLUTIONS

#### 󠀁[AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS QUESTIONS ANSWERS SOLUTIONS  download click here](https://drive.google.com/file/d/1WLAeR0-Zb199VmsPMrNZXQJrkooAfMhn/view?usp=sharing)󠁿

**1. Which of the statements about the reaction below are incorrect?**

2PbO(s) + C(s) → 2Pb(s) + CO_(2)(g)

**(a) Lead is getting reduced**

**(b) Carbon Dioxide is getting oxidised**

**(c) Carbon is getting oxidised**

**(d) Lead oxide is getting reduced**

**        (i) (a) and (b)**

**       (ii) (a) and (c)**

**        (iii) (a), (b) and (c)**

**        (iv) all the above**

**Solution:**

(i) (a) and (b)

Explanation: (a) Because Oxygen is being removed and (b) Because the removed oxygen
from Lead is added to the elemental Carbon.

**2.  Fe_(2)O_(3 )+ 2Al → Al_(2)O_(3 )+ 2Fe**

**The above reaction is an example of a**

 1. **Combination reaction**
 2. **Double displacement reaction**
 3. **Decomposition reaction**
 4. **Displacement reaction**

**Solution:**

The answer is 4. Displacement reaction.0

Explanation: The Oxygen from the Ferrous oxide is getting displaced to the Aluminium
metal to form Aluminium Oxide. In this reaction, Aluminum is a more reactive metal
than Fe. Therefore, Al will displace Fe from its oxide. This type of chemical reaction,
called displacement reaction, is in which one of the elements displaces another.
Here, less reactive metal is displaced by more reactive metal. Since one-time displacement
is occurring, it is called a single displacement reaction.

 

**3. What happens when dilute hydrochloric acid is added to iron fillings? Tick 
the correct answer.**

 1. **Hydrogen gas and Iron chloride are produced.**
 2. **Chlorine gas and Iron hydroxide are produced.**
 3. **No reaction takes place.**
 4. **Iron salt and water are produced.**

**Solution:**

 1. Hydrogen gas and Iron chloride are produced.

Explanation: The Chlorine from Hydrogen chloride is displaced by the Iron fillings
to undergo the following reaction.

2HCl + Fe → FeCl_(2 )+ H_(2)
 **4. What is a balanced chemical equation? Why should
a chemical equation be balanced?**

**Solution:**

A balanced equation is the one in which number of different atoms on both the reactant
and product sides are equal. Balancing chemical equations is necessary for the reaction
should obey The Law of Conservation of mass. Balancing the chemical equation has
no defined method and is purely a trial-and-error attempt.

 

5.  Translate the following statements into chemical equations and balance them.
**(
a) Hydrogen gas combines with nitrogen to form ammonia.**

**(b) Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.**

**(c) Barium chloride reacts with aluminium sulphate to give Aluminium chloride 
and a precipitate of barium sulphate.**

**(d) Potassium metal reacts with water to give potassium hydroxide and Hydrogen
gas.**

**Solution:**

(a) Unbalanced: H_(2 )+ N_(2 )→ NH_(3)

Balanced: 3H_(2 )+ N_(2 )→ 2NH_(3)

(b) Unbalanced: H_(2)S + O_(2 )→ H_(2)O + SO_(2)

Balanced: 2H_(2)S + 3O_(2 )→ 2H_(2)O + 2SO_(2)
 (c)  Unbalanced:BaCl_(2 )+ Al_(2)(
SO_(4))_(3 )→ AlCl_(3 )+ BaSO_(4)

Balanced: 3BaCl_(2 )+ Al_(2)(SO_(4))_(3 )→ 2AlCl_(3 )+ 3BaSO_(4)
 (d) Unbalanced:
K + H_(2)O → KOH + H_(2)

Balanced:  2K + 2H_(2)O → 2KOH + H_(2)

**6. Balance the following chemical equations. **

**(a) HNO_(3) + Ca(OH)_(2) → Ca(NO_(3))_(2) + H_(2)O **

**(b) NaOH + H_(2)SO_(4) → Na_(2)SO_(4) + H_(2)O**

**(c) NaCl + AgNO_(3) → AgCl + NaNO_(3)**

**(d) BaCl_(2) + H_(2)SO_(4) → BaSO_(4) + HCl**

**Solution:**

(a) 2HNO_(3 )+ Ca(OH)_(2 )→ Ca(NO_(3))_(2 )+ 2H_(2)O
 (b) 2NaOH + H_(2)SO_(4 )→ 
Na_(2)SO_(4 )+ 2H_(2)O

(c) NaCl + AgNO_(3 )→ AgCl + NaNO_(3)

(d) BaCl_(2 )+ H_(2)SO_(4 )→ BaSO_(4 )+ 2HCl

 

**7. Write the balanced chemical equation for the following reactions.**

**Calcium hydroxide + Carbon dioxide —-> Calcium carbonate + Water**

**Zinc + Silver nitrate —-> Zinc nitrate + Silver**

**Aluminium + Copper chloride —-> Aluminium chloride + Copper**

**Barium chloride + Potassium sulphate —-> Barium sulphate + Potassium chloride**

**Solution:**

2Ca(OH)_(2 )+ 2CO_(2 )→ 2CaCO_(3 )+ 2H_(2)O

Zn + 2AgNO_(3 )→ Zn(NO_(3))_(2 )+ 2Ag

2Al + 3CuCl_(2 )→ 2AlCl_(3 )+ 3Cu

BaCl_(2 )+ K_(2)SO_(4 )→ BaSO_(4 )+ 2KCl

**8. Write a balanced chemical equation for the following and identify the type 
of reaction of each case.**

**KBr + BaI_(2 )→ KI + BaBr_(2)**

**ZnCO_(3 )→ ZnO + CO_(2)**

**H_(2 )+ Cl_(2) → HCl**

**Mg + HCl → MgCl_(2 )+ H_(2)**

**Solution:**

2KBr + BaI_(2 )→ 2KI + BaBr_(2) (Double Displacement Reaction)
 ZnCO_(3 )→ ZnO +
CO_(2) (Decomposition Reaction) H_(2) + Cl_(2) → 2HCl (Combination Reaction)

Mg + 2HCl → MgCl_(2 )+ H_(2) (Displacement Reaction)

**9. What is meant by exothermic and endothermic reactions? Give examples.**

**Solution:**

An endothermic reaction occurs when energy is absorbed from the surroundings in 
the form of heat (For example, Photosynthesis, melting of ice, evaporation). Conversely,
an exothermic reaction is one in which energy is released from the system into the
surroundings (Examples: Explosions, concrete setting, nuclear fission and fusion).

Exothermic Reaction: The reactions in which heat is evolved along with the formation
of new products are called exothermic reactions. In these reactions the energy of
the reactants is more than that of the products, so energy is released to complete
the reaction.

Energy of reactants > Energy of products

Example: Complete combustion of methane gas produces carbon dioxide and water along
with heat and light.

CH4( g)+2O2( g)→CO2+2H2O+heat+light

Another example of exothermic reactions is respiration and decomposition of vegetable
matter.

Endothermic Reaction: The reactions in which energy is absorbed by the reactants
to carry on the reaction are called endothermic reactions. In this type of reaction,
the energy of the reactants is less than that of the products, so energy is needed
and absorbed.

Energy of reactants <Energy of products

Example: Process of Photosynthesis, where plants absorb sunlight in the presence
of carbon dioxide and water and make their food in the form of glucose and release
oxygen.

6CO2(g)+6H2O(l)−→sunlight–  C6H12O4(aq) +6O2(g)

**10. Why is respiration considered to be an exothermic reaction?**

**Solution:**

For the survival of life, we require energy. We obtain this energy from the food
we eat. The food molecules, through the process of digestion, is broken down into
simpler molecule like glucose. These substances come in contact with the Oxygen 
present in our body cells to form Carbon dioxide and water along with a certain 
amount of energy (Respiration process). Since the energy is in the form of heat (
that maintains our body temperature), respiration is considered to be an exothermic
reaction. The reaction taking place is:

C_(6)H_(12)O_(6 )+ 6O_(2 )→ 6CO_(2 )+ 6H_(2)O + Energy

 

**11. Why are decomposition reactions called the opposite of Combination reactions?
Write equations for decomposition reactions.**

**Solution:**

Combination reaction is said to be the reaction between two or more molecules to
form a larger molecule; whereas the decomposition reaction is defined as the splitting
of larger molecules into two or more smaller molecules. This essentially explains
that the decomposition reaction is the opposite of the combination reaction.

In most cases, the decomposition reaction is endothermic since the heat from the
surrounding or induced heat is used to break the bonds of the larger molecule. A
few examples of decomposition reactions are

ZnCO_(3) → ZnO + CO_(2)

CaCO_(3) + Energy → CaO + CO_(2)

2HgO → 2Hg + O_(2)

 

**12. Write one equation each for decomposition reactions in which energy is supplied
in the form of heat, light or electricity.**

**Solution:**

(a) Thermal decomposition reaction (Thermolysis)

Decomposition of potassium chlorate: When heated strongly, potassium chlorate decomposes
into potassium chloride and oxygen. This reaction is used for the preparation of
oxygen.

2KClO_(3 )+ Heat → 2KCl + 3O_(2)

(b) Electrolytic decomposition reaction (Electrolysis)

Decomposition of sodium chloride: On passing electricity through molten sodium chloride,
it decomposes into sodium and chlorine.

(c) Photodecomposition reaction (Photolysis)

Decomposition of hydrogen peroxide: In the presence of light, hydrogen peroxide 
decomposes into water and oxygen.

**13.  What is the difference between displacement and double displacement reactions?
Write relevant equations for the above.**

**Solution:**

A displacement reaction is one when a more reactive substance displaces a less reactive
one from its salt solution, whereas a double displacement reaction is one where 
a mutual exchange of ions happens between two compounds.

In a displacement reaction, only a single displacement takes place, whereas in the
double displacement reaction, as the name suggests, two displacement takes place
between the molecules.

Example:

Displacement reaction

Mg + 2HCl → MgCl_(2 )+ H_(2)

Double displacement reaction

2KBr + BaI_(2) → 2KI + BaBr_(2)

**14. In the refining of Silver, the recovery of silver from Silver nitrate solution
involves displacement reaction by Copper metal. Write down the reaction involved.**

**Solution:**

Cu(s) + 2AgNO_(3)(aq) → Cu(NO_(3))_(2)(aq) + 2Ag(s)
 **15. What do you mean by a
precipitation reaction? Explain by giving examples.**

**Solution:**

When two solutions containing soluble salts are combined, a double displacement 
reaction takes place in which the ions are exchanged between the compounds. When
one of such compounds formed is in solid form (that is insoluble in aqua), then 
it settles down at the bottom of the container. This solid is known as the precipitate
and the respective reaction is termed as the precipitation reaction. A few examples
of precipitation reactions are

CdSO_(4)(aq) + K_(2)S(aq) → CdS(s) + K_(2)SO_(4)(aq)

2NaOH(aq) + MgCl_(2)(aq) → 2NaCl(aq) + Mg(OH)_(2)(s)

**16. Explain the following in terms of the gain of oxygen with two examples each.**

**(a) Oxidation**

**(b) Reduction**

**Solution:**

(a) In a chemical reaction, when the oxygen is added to the element to form its 
respective oxide it is the element being oxidised. Example:

4Na(s) + O_(2)(g) → 2Na_(2)O(s)

H_(2)S + O_(2 )→ H_(2)O + SO_(2)
 (b) In a chemical reaction, when the oxygen is
removed from the compound, then it is said to be reduced. Example: CuO(s) + H_(2)(
g) → Cu(s) + H_(2)O(l)

2HgO → 2Hg + O_(2)
 **17. A shiny brown coloured element ‘X’ on heating in the air
becomes black in colour. Name the element ‘X’ and the black-coloured compound formed.****
Solution:**

The shiny brown-coloured element is Copper metal (Cu). When the metal is heated 
in air, it reacts with atmospheric oxygen to form copper oxide. Hence, the black-
coloured compound is copper oxide.

2Cu(s) + O_(2)(g) → 2CuO(s)
 **18) Why do we apply paint on iron articles?** **Solution:**

Iron articles are painted to prevent them from rusting. When left unpainted, the
metal surface comes in contact with the atmospheric oxygen and in the presence of
moisture it from Iron(III) oxide. But if painted, the surface does not come in contact
with moisture and air, thus prevents Rusting.

**19) Oil and Fat containing food items are flushed with Nitrogen. Why?**

**Solution:**

The main purpose of flushing Nitrogen into food packets that contain oil and fat
items is to prevent Rancidity which occurs when the oil or fat reacts with the oxygen
letting out an unpleasant smell and taste. Therefore, by flushing Nitrogen, an unreactive
surrounding is created, thus preventing rancidity.
 **20) Explain the following 
terms with one example each.**

**(a) Corrosion**

**(b) Rancidity**

**Solution:**

(a) Corrosion is a process where a refined metal is oxidised by atmospheric oxygen
to form a more stable compound, such as oxides. The metal gradually degrades during
the corrosion process. Rusting of iron is a good example of corrosion where the 
iron is converted to Iron oxide. Millions of dollars are spent annually in preventing
rusting from bridges and other monuments.

(b) The condition produced by the aerial oxidation of the oil and fat present in
the food material that produces an unpleasant taste and smell. The rancidity is 
retarded when the food is kept inside the refrigerator since the low temperature
does not promote the oxidation reaction.

## **In-text questions – answers : AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS SOLUTIONS

**1. Why should a magnesium ribbon be cleaned before burning in the air?**

**Solution:**

Magnesium ribbon should be cleaned before burning in air because Magnesium metal
reacts with the atmospheric oxygen and forms Magnesium Oxide (MgO) layer which is
a very stable compound. In order to prevent further reactions with Oxygen, it is
therefore necessary to clean the ribbon by to remove the layer of MgO.

**2. Write a balanced equation for the following chemical reactions.**

**i) Hydrogen + Chloride —-> Hydrogen chloride**

**ii) Barium chloride + Aluminium sulphate —-> Barium sulphate + Aluminium chloride**

**iii) Sodium + Water —-> Sodium hydroxide + Hydrogen**

**Solution:**

i) H_(2 )+ Cl_(2 )→ 2HCl

ii) 3BaCl_(2 )+ Al_(2)(SO_(4))_(3 )→3BaSO_(4 )+ 2AlCl_(3 )

iii) 2Na + 2H_(2)O → 2NaOH + H_(2)

**3. Write a balanced chemical equation with state symbols for the following reactions**

**i) Solutions of Barium chloride and Sodium sulphate in water react to give insoluble
Barium sulphate and solution of Sodium chloride.**

**ii) Sodium hydroxide solution in water reacts with the hydrochloric acid solution
to produce Sodium chloride solution and water.**

**Solution:**

i) BaCl_(2 )+ Na_(2)SO_(4 )→ BaSO_(4 )+ 2NaCl

ii) NaOH + HCl → NaCl + H_(2)O

 

## **In-text questions – answers : ****AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS SOLUTIONS**

## ** **

**1. A solution of a substance, ‘X,’ is used for whitewashing. **

**(i) Name the substance ‘X’ and write its formula. **

**(ii) Write the reaction of the substance ‘X’ named in (i) above with water. **

**Solution:**

i) The substance ‘X’ which is used in whitewashing is quick lime or **Calcium Oxide**
and its formula is **CaO**.

ii) CaO + H_(2)O → Ca(OH)_(2)

**2. Why is the amount of gas collected in one of the test tubes in Activity 1.7
double the amount collected in the other? Name this gas.**

**Solution:**

In activity 1.7, gas collected in one of the test tubes is double of the amount 
collected in the other because water gets hydrolysed to release H_(2) and O_(2) 
gas. Here, after electrolysis two molecules of Hydrogen and one molecule of oxygen
gas are released; hence, the amount of Hydrogen collected would be double than that
of oxygen.

## **In-text questions – answers : ****AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS SOLUTIONS**

## ** **

**1. Why does the colour of copper sulphate solution change when an iron nail is
dipped in it?**

**Solution:**

When an iron nail is dipped in the copper sulphate solution, iron displaces copper
from the copper sulphate because iron is more reactive than copper. Therefore, the
colour of the copper sulphate solution changes. The reaction is

Fe + CuSO_(4) → FeSO_(4) + Cu

** 2. ****Give an example of a double displacement reaction other than the one given
in Activity 1.10.**

** ****Solution:**

Reaction Between silver nitrate (AgNO_(3)) and Sodium chloride (NaCl) is an example
of a double displacement reaction. During the reaction, negative and positive ions
trade positions as a result of the formation of white silver chloride precipitate.
The chemical reaction is given below.

Ag^(+) + NO_(3)^(–) + Na^(+) + Cl^(– )→ AgCl + Na^(+) + NO_(3)^(–)

**3. Identify the substances that are oxidised and that are reduced in the following
equation.**

**i) **4Na(s) + O_(2)(g) → 2Na_(2)O(s)

**ii) **CuO(s) + H_(2)(g) → Cu(s) + H_(2)O(l)

**Solution:**

 

The Sodium (Na) in the first equation is getting oxidized with the addition of Oxygen(
O_(2)), and the Copper (Cu) in the second equation is reduced due to the addition
of Hydrogen (H_(2)).

#### 󠀁[AP 10TH CLASS PHYSICS CHEMICAL REACTIONS AND EQUATIONS QUESTIONS ANSWERS SOLUTIONS  download click here](https://drive.google.com/file/d/1WLAeR0-Zb199VmsPMrNZXQJrkooAfMhn/view?usp=sharing)󠁿

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