AP 10th Class Physical Science 1st Lesson Questions and Answers Chemical Reactions and Equations

AP State Board new syllabus AP Board Solutions Class 10 Physics 1st Lesson Chemical Reactions and Equations Questions and Answers.

10th Class Physical Science 1st Lesson Chemical Reactions and Equations Questions and Answers

10th Class Physics 1st Lesson Questions and Answers (Exercise)

Question 1.
Which of the statements about the reaction below are incorrect ?
2PbO(s) + C(s) → 2PbO(s) + CO₂(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
Answer:
i) (a) and (b) are incorrect statements because ‘Pb’ and ‘CO₂’ are products and not reactants.

Question 2.
Fe₂O₃ + 2Al → Al₂O₃ + 2Fe
The above reaction is an example of a
a) combination reaction.
b) double displacement reaction.
c) decomposition reaction.
d) displacement reaction.
Answer:
d) Al is displacing iron from iron (III) oxide.
Therefore, it is a displacement and redox reaction.

Question 3.
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
a) Hydrogen gas and iron chloride are produced.
b) Chlorine gas and iron hydroxide are produced.
c) No reaction takes place.
d) Iron salt and water are produced.
Answer:
a) Fe_(s) + 2HCl_(dil) → FeCl_2(aq) + H_2(g)
Hydrogen gas and iron (II) chloride are produced.

Question 4.
What is a balanced chemical equation? Why should chemical equations be balanced?
Answer:
Balanced chemical equation means total number of atoms of each element should be equal on both sides of the reaction.
For example, magnesium and oxygen combine, when heated to from a single compound, magnesium oxide
2 Mg_(s) + O_2(g) → 2MgO_(s)
The reaction should be balanced because matter can neither be created nor be destroyed. The total mass of reactants should be equal to the total mass of products.

Question 5.
Translate the following statements into chemical equations and then balance them.
a) Hydrogen gas combines with nitrogen to form ammonia.
b) Hydrogen sulphide gas burns in 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.
Answer:
a) 3H_2(g) + N_{2 (g)} → 2NH_3(g)
b) 2H₂S_(g) + 3O_2(g) → 2H₂O_(l) + 2SO_2(g)
c) 3BaCl_2(aq) + Al₂(SO₄)_(aq) → 3BaSO_4(s) (s) + 2AlCl_3(aq)
d) 2K_(s) + 2H₂O_(l) → 2KOH_(aq) + H_2(g)

Question 6.
Balance the following chemical equations.
a) HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
b) NaOH + H₂SO₄ → Na₂SO₄ + H₂O
c) NaCl + AgNO₃ → AgCl + NaNO₃
d) BaCl₂ + H₂SO₄ → BaSO₄ + HCl
Answer:
a) 2HNO_3(aq) + Ca(OH)_2(aq) → Ca(NO₃)_2(aq) + 2H₂O_(l)
b) 2NaOH_(aq) + H₂SO_4(aq) → Na₂SO_4(aq) + H₂O_(l)
c) NaCl_(aq) + AgNO_3(aq) → AgCl_(s) + NaNO_{3 (aq)}
d) BaCl_2(aq) + H₂SO_4(aq) → BaSO_4(s) + 2HCl_aq

Question 7.
Write the balanced chemical equations for the following reactions.
a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
b) Zinc + Silver nitrate → Zinc nitrate + Silver
c) Aluminium + Copper chloride → Aluminium chloride + Copper
d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Answer:
a) Ca (OH)_2(aq) + CO_2(g) → CaCO_3(s) + H₂O_(l)
b) Zn_(s) + 2AgNO_3(aq) → Zn(NO₃)_2(aq) + 2 Ag_(s)
c) 2Al_(s) + 3CuCl_2(aq) → 2AlCl_3(aq) + 3 Cu_(s)
d) BaCl_2(aq) + K₂SO_4(aq) → BaSO_4(s) + 2KCl_(aq)

Question 8.
Write the balanced chemical equation for the following and identify the type of reaction in each case.
a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
b) Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)
c) Hydrogen(g) + Chlorine(g) → Hydrogen chloride(g)
d) Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)
Answer:
a) 2KBr_(aq) + BaI_2(aq) → 2KI_(aq) + BaBr_2(s)
Type of reaction : Double displacement reaction.

b) ZnCO_3(s) → ZnO_(s) + CO_2(g)
Type of reaction : Decomposition reaction.

c) H_2(g) + Cl_2(g) → 2HCl_(g)
Type of reaction : Combination reaction and redox reaction.

d) Mg_(s) + 2HCl_(aq) → MgCl_2(aq) + H_2(g)
Type of reaction : Displacement reaction and redox reaction.

Question 9.
What does one mean by exothermic and endothermic reactions ? Give examples.
Answer:
Exothermic reactions are those reactions in which heat is evolved.
Examples: C_(s) + O_2(g) → CO_2(g) + Heat
CH_4(g) + 2O_2(g) → CO_2(g) + 2H₂O + Heat

Endothermic reactions are those reactions in which heat is absorbed.
Examples :

Question 10.
Why is respiration considered an exothermic reaction ? Explain.
Answer:
During respiration, glucose combines with oxygen in the calls of our body and provides energy. As energy is released during respiration, therefore, respiration is regarded as exothermic reaction.
C₆H₁₂ O_6(aq) + 6O_2(g) → 6CO_2(g) + 6H₂O_(l) +Energy

Question 11.
Why are decomposition reactions called the opposite of combination reactions ? Write equations for these reactions.
Answer:
In decomposition reactions, a compound is broken down into simpler compounds or elements.

Combination Reaction is a reaction in which two or more elements or compounds combine to form new compound.

Thus, decomposition and combination reactions are opposite to each other.

Question 12.
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer:

Question 13.
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Answer:
Displacement Reaction : Those reactions in which, more reactive metal displaces less reactive metal from its salt solution are called displacement reactions.
Example : Fe_(s) + CuSO_4(aq) → FeSO_4(aq) + Cu_(s)

Double Displacement Reaction : Those reactions in which two compounds exchange their ions to form two new compounds are called double displacement reactions. It is redox reaction.
Example : HCl_(aq) + NaOH_(aq) → NaCl_(aq) + H₂O_(l)

Question 14.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Answer:

Thus, silver meted can be recovered.

Question 15.
What do you mean by a precipitation reaction ? Explain by giving examples.
Answer:
Those reactions in which two compounds react to form insoluble compound, which is called precipitate, are called precipitation reactions.
E.g.: When solutions of silver nitrate and sodium chloride are mixed, white precipitate of silver chloride is formed
AgNO_3(aq) + NaCl_(aq) → AgCl_(s) + NaNO_3(aq)
On adding dilute hydrochloric acid to the aqueous solution of lead nitrate, precipitate of lead chloride is formed.
Pb(NO₃)_2(aq) + 2HCl_(aq) → PbCl_2(s) + 2HNO_3(aq)

Question 16.
Explain the following in terms of gain or loss of oxygen with two examples each,
a) Oxidation
b) Reduction
Answer:
a) Oxidation : It is a process in which gain of oxygen takes place

b) Reduction : It is a process in which removal of oxygen takes place

Question 17.
A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Answer:
Element ‘X’ is Copper
Copper gets oxidised to copper oxide which is black in colour

Question 18.
Why do we apply paint on iron articles ?
Answer:
By applying paint on iron articles, they can be prevented from corrosion (rusting). Since paint does not allow oxygen (from air) and water (moisture) to come in contact with the surface of iron.

Question 19.
Oil and fat containing food items are flushed with nitrogen Why ?
Answer:
The micro organisms present in the oxygen of the air oxidise the fat and oil present in food items to make such compounds which have bad smell and taste, thus, they become rancid. Rushing with nitrogen cuts off oxygen which protects the food from rancidity.

Question 20.
Explain the following terms with one example each.
a) Corrosion
b) Rancidity
Answer:
a) Corrosion : The phenomenon due to which open surface of the metals are slowly eaten away by the reaction of air, water and chemicals present in the atmosphere is called corrosion.
Example :
i) Corrosion of iron is called rusting
ii) Copper objects acquire a green coating of basic copper carbonate.

b) Rancidity : It is the process of slow oxidation of oil and fat present in the food materials resulting in the change of smell and taste in them.
Example : A food containing oil and fat if left for along time develops bad taste and bad smell and gets spoiled.

10th Class PS 1st Lesson Questions and Answers (InText)

Page No. 14

Question 1.
Why should a magnesium ribbon be cleaned before burning in air ?
Answer:
Magnesium ribbon should be cleaned with sand paper before burning in air order to remove white layer of magnesium oxide (MgO) from its surface which hinders the burning of magnesium.

Question 2.
Write the balanced equation for the following chemical reactions.
i) Hydrogen + Chlorine → Hydrogen chloride
ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
iii) Sodium + Water → Sodium hydroxide + Hydrogen
Answer:
i) H_2(g) + Cl_2(g) → 2HCl_2(g)
ii) 3BaCl_2(aq) + Al₂(SO₄)_3(aq) → 3BaSO_4(s) + 2AlCl_3(aq)
iii) 2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g)

Question 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 the solution of sodium chloride.
ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Answer:
i) BaCl_2(aq) + Na₂SO_4(aq) → BaSO_4(s) + 2NaCl_(aq)
ii) NaOH_(aq) + HCl_(aq) → NaCl_(aq) + H₂O _(l)

Page No. 22

Question 4.
A solution of a substance ‘X’ is used for white washing.
i) Name the substance ‘X’ and write its formula.
ii) Write the reaction of the substance ‘X’ named in (i) above with water.
Answer:
i) For white washing a solution quick lime is used. The substance ‘X’ is quick lime and its formula is CaO (Calcium oxide)

ii) When quick-lime reacts with water, the following reactions takes place.

Question 5.
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other ? Name this gas.
Answer:
During electrolysis, water decomposes to form hydrogen and oxygen gases.

In the above reaction, the balanced chemical equation shows that an electrolysis, the water decomposes to form hydrogen and oxygen in the ratio of 2 : 1 by volume.

Page No. 28

Question 6.
Why does the colour of copper sulphate solution change when an iron nail is dipped in it ?
Answer:
Iron is more reactive element than copper. When an iron nail is dipped in copper sulphate solution which is blue in colour, iron being more reactive than copper displaces copper from copper sulphate and forms, iron (II) sulphate which is green in colour.

Question 7.
Give an example of a double displacement reaction other than the one given in Activity 1.10.
Answer:
AgNO₃ (aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)

Question 8.
Identify the substances that are oxidised and the substances that are reduced in the following reactions.
i) 4Na(s) + O₂(g) → 2Na₂O(s)
ii) CuO(s) + H₂(g) → Cu(s) + H₂O(I)
Answer:
i) Na has gained oxygen and forms Na20. So, Na is oxidised and O₂ is reduced.
ii) CuO has lost oxygen and forms Cu. So, CuO is reduced and H₂ which has gained oxygen is oxidised.

Group Activity (Page No : 34)

• Take four beakers and label them as A, B, C and D.
• Put 25 ml of water in A B and C beakers and copper sulphate solution in beaker D.
• Measure and record the temperature of each liquid contained in the beakers above.
• Add two spatulas of potassium sulphate, ammonium nitrate, anhydrous copper sulphate and fine iron fillings to beakers A, B, C and D respectively and stir.
• Finally measure and record the temperature of each of the mixture above.

Find out which reactions are exothermic and which ones are endothermic in nature.
Answer:

1. Take four beakers and label them as A, B, C and D.
2. Put 25 ml of water in A, B and C beakers and copper sulphate solution in beaker D.
3. Measure and record the temperature of each liquid contained in the beakers above.
4. Add two spatulas of potassium sulphate, ammonium nitrate, anhydrous copper sulphate and fine iron fillings to beakers A, B, C and D respectively and stir.
5. Finally measure and record the temperature of each of the mixture above.
6. In A, C and D beakers heat is evolved during a reaction the reaction can be exothermic reaction.
7. In B beaker heat is absorbed during a reaction the reaction can be endothermic reaction

AP 10th Class Physical Science Chapter 1 Questions and Answers (Lab Activities)

Activity – 1.1 (Page No. 4)

Question 1.
Write the procedure and observations in the reaction of magnesium and oxygen.
Answer:
Aim : To show that burning of magnesium ribbon in air is a combination reaction. Materials required : Magnesium wire, Tong, Burner.

Procedure:
1) Take a strip of magnesium ribbon and hold it with the help of tong.
2) Introduce it into the flame of the burner.
Observation Magnesium ribbon burns with a dazzling white flame and changes into a white powder.
Chemical Reaction :
Conclusion : Burning of magnesium in presence of oxygen to form magnesium oxide is a combination reaction and an exothermic process because heat and light are produced.

Activity – 1.2 (Page, No. 6)

Question 2.
Take lead nitrate solution in a test tube.
Add potassium iodide solution to this. What do you observe? How do you classify the reaction ?
Answer:

1. When you add potassium iodide (KI) solution to lead nitrate (Pb(NO₃))₂ solution in a test tube, you will observe the formation of a yellow precipitate.
2. This reaction is a classic example of a double displacement reaction, also known as a precipitation reaction.
3. The balanced chemical equation for this reaction is as follows :
   Pb(NO₃))₂(aq) + 2KI(aq) → Pbl₂(s) + 2KNO₃(aq)

Activity – 1.3 (Page, No. 6)

Question 3.
Write an activity to show the change in temperature in a chemical reaction. (Or) Take a few zinc granules in a conical flask or a test tube. Add dilute hydrochloric acid or sulphuric acid to this (Figure).
Do you observe anything happening around the zinc granules ?
Touch the conical flask or test tube. Is there any change in its temperature ?
Answer:
Aim : To formation of hydrogen gas by the action of dilute sulphuric acid on Zinc. Materials required Conical flask, Zinc granules, Dilute sulphuric acid, Glass tube, Cork.
Procedure :

1. Take a few zinc granules in a conical flask.
2. Add dilute sulphuric acid to this.
3. Observe happening around the zinc granules.
4. Touch the conical flask and observe any change in its temperature.

Observation : Formation of hydrogen gas the action of dilute sulphuric acid on zinc. It is an exothermic process because heat is evolved.
Chemical Reaction : Zn + H₂SO₄ → ZnSO₄ + H₂
Conclusion : This is exothermic process because heat is evolved.

Activity – 1.4 (Page, No. 14)

Question 4.
Write an activity to show a chemical combination reaction.
Answer:
Aim : To show that combination reaction between calcium oxide and water is an exothermic process.
Materials required : Quick lime (Calcium oxide), Water, Beaker
Procedure :
1) Take a small amount of calcium
oxide or quick lime in a beaker.
2) Slowly add water to this.
3) Touch the beaker.
4) Note down the observations.

Observations : Calcium oxide reacts with water vigorously to form calcium hydroxide with the evolution of heat.

Chemical Reaction :
Conclusion : The reaction between CaO (calcium oxide) and H₂O is a combination reaction. It is an exothermic process because heat is evolved.

Activity – 1.5 (Page. No. 18)

Question 5.
Write an activity to show a decomposition reaction.
Answer:
Aim : To show thermal decomposition reaction of ferrous sulphate.
Materials required : Ferrous sulphate crystals, dry test tube, burner.

Procedure :

1. Take 2g of ferrous sulphate crystals in a dry test tube.
2. Note the colour of the ferrous sulphatecrystals.
3. Heat the boiling tube over the flame of a burner for some time.
4. Observe the colour of the crystals after heating.

Observation : The pale green colour of ferrous sulphate crystals changes to reddish brown ferric oxide and smell of burning sulphur is observed.
Chemical Reaction :
Ferrous sulphate Ferric oxide
Conclusion : Heating of ferrous sulphate is a thermal decomposition because ferrous sulphate braks into simpler compounds Fe₂O₃, SO₂ and SO₃.

Activity – 1.6 (Page. No. 18)

Question 6.
a) Design an activity to demonstrate the decomposition reaction of lead nitrate.
b) Draw labelled diagram of the exp : ntal setup. List two main observations.
c) Write balanced chemical equation for the reaction stating the physical state of the reactant and products.
Answer:
a) Activity :

1. Take a boiling tube and put about 3g lead nitrate powder in it.
2. Hold the boiling tube carefully with a pair of tongs.
3. Now, heat the tube over a flame.

b) Observations :

1. Brown fumes of nitrogen dioxide gas is observed.
2. Lead oxide, a yellow compound is formed.

Activity – 1.7 (Page. No. 20)

Question 7.
plain electrolysis of water with an activity (or) With the help of an activity explain that H₂ and O₂ are released when an electric current is passed through vater.
Answer:
Aim : To demonstrate electrolysis of water.
Materials required : Plastic mug, drilling machine, two graduated measuring cylinder, carbon electrodes, 6 volt battery, dil H₂SO₄, Water.
Procedure :

1. Take a plastic mug. Drill two holes at its base and fit rubber stoppers in these holes. Insert carbon electrodes in these rubber stoppers as shown in figure.
2. Connect these electrodes to a 6-volt battery.
3. Fill the mug with water such that the electrodes are immersed. Add a few drops of dilute sulphuric acid to the water.
4. Take two test tubes filled with water and invert them over the two carbon electrodes.
5. Switch on the current and leave the apparatus undisturbed for some time.
6. You will observe the formation of bubbles at both the electrodes. These bubbles displace water in the test tubes.
7. Observe the volume of gases collected in respective test tubes.
8. Once the test tubes are filled with the respective gases, remove them carefully.
9. Test these gases one by one by bringing a burning candle close to the mouth of the test tubes.

Observation : The volume of one gases, i.e., hydrogen is twice the volume of other gas. One of the gases catches fire and burns with ‘pop’ sound where as in other gas, e.g. oxygen, match-stick burns brightly.
Conclusion : Water on electrolysis decomposes to hydrogen and oxygen gas.

Activity – 1.8 (Page. No. 20)

Question 8.
Write an activity to show the decomposition reaction by using light.
Answer:

Aim : To show photochemical decomposition of silver chloride.
Materials required : AgNO_3(aq), NaCl_(aq), test tubes.
Procedure :

1. Take about 2g silver chloride in a china dish.
2. Observe the colour of silver chloride.
3. Place this china dish in sunlight for some time.
4. Observe the colour of the silver chloride after some time.

Observation : White silver chloride turns grey in sunlight because silver metal is formed.

Chemical Reaction :
Conclusion: Decomposition of silver chloride in presence of sunlight is photochemical decomposition reaction.

Activity – 1.9 (Page. No. 22)

Question 9.
Write an activity to show the chemical displacement reaction.
Answer:
Aim : To show reaction between Iron nails and copper sulphate solution.
Materials required : Copper sulphate solution, Iron nail, Test tube, Thread, Stand.

Procedure :

1. Take three iron nails and clean them by rubbing with sand paper.
2. Take two test tubes marked as (a) and (b). In each test tube, take about 10 ml copper sulphate solution.
3. Tie two iron nails with a thread and immerse them carefully in the copper sulphate solution in test tube (b) for about 20 minutes. Keep one iron nail a side for comparison.
4. After 20 minutes, take out the iron nails from the copper sulphate solution.
5. Compare the intensity of the blue colour of copper sulphate solution in test tubes (a) and (b).
6. Also, compare the colour of the iron nails dipped in the copper sulphate solution with the one kept aside.

Observation : The iron nail become brownish in colour and the blue colour of copper sulphate solution fades.
Chemical Equation :
Conclusion : In this reaction, iron has displaced or removed another element, copper, from copper sulphate solution.

Activity – 1.10 (Page. No. 24)

Question 10.
Explain double displacement reaction with an activity.
Answer:
Aim : To show reaction between sodium sulphate solution and barium chloride solution is double displacement reaction (precipitation reaction)
Materials required : Barium chloride solution, sodium sulphate solution, two test tubes.
Procedure:

1. Take about 3 ml of sodium sulphate solution in a test tube.
2. In another test tube, take about 3 ml of barium chloride solution.
3. Mix the two solutions.
   
   Observation : White precipitate is formed.
   Chemical Reaction :
   Conclusion : Reaction between sodium sulphate solution and barium chloride solution is double displacement reaction. It is also called precipitation reaction.

Activity – 1.11 (Page. No. 26)

Question 11.
Write an activity to understand the Oxidation and Reduction reaction.
Answer:
Aim : To prepare copper oxide and to show the redox reaction of copper oxide with hydrogen gas.
Materials required : Copper powder, China dish, Wire guaze, Tripod stand, Burner.
Procedure:

1. Heat a china dish containing about 1 g copper powder.
2. Pass the air over heated copper powder. Note down the observations.
3. Now pass the hydrogen gas over the heated copper oxide. Record the observations after sometime.
   
   Observation : Copper reacts with Air (oxygen) on heating to form copper oxide which is black. Now pass the hydrogen gas over the heated copper oxide, the black coating on the surface turns pink (reddish brown).
   Chemical Reaction :

Conclusion : The reaction between copper oxide and hydrogen is redox reaction. Copper oxide is oxidising agent whereas hydrogen is reducing agent.