Telangana SCERT Class 9 Physical Science Chapter 7 Solution – Atoms, Molecules And Chemical Reactions. Here in this post we provides Class 9 Physical Science Atoms, Molecules And Chemical Reactions Telangana State Board Solution. Telangana State Board English Class IX Medium Students can download this Solution to Solve out Improve Your Learning Questions and Answers.
Telangana State Board Class 9 Physical Science Chapter 7 Atoms, Molecules And Chemical Reactions Solution:
CHAPTER: – 7
Atoms, Molecules And Chemical Reactions
Reflections on concepts
1) Explain the process and precautions in verifying law of conservation of mass.
Ans: – The reaction between the barium chloride and aluminium sulphate proves the laws of conservation of mass as in before and after the reaction the mass of the reactants and products same which clarify that mass can not be created or destroyed.
2) In a class, a teacher asked students to write themolecular formula of oxygen Samhita wrote the formula as O2 and Priyanka as O. which one is correct? State the reason.
Ans: – As Samhita wrote the formula O2 which is wright as oxygen are diatomic in air.
3) Find out the chemical names and formulae for the following common household substances. (AS-1)
a) common salt b) baking soda c) washing soda d) vinegar.
Ans: – The chemical name of salt is sodium chloride, the chemical name of baking soda is sodium bicarbonate, sodium carbonate is the chemical name of washing soda and the chemical name of vinegar is acetic acid.
4) Calculate the mass of the following (AS-1)
a) 0.5 mole of N2gas. b) 0.5 mole of N atoms.
c) 3.011 x 1023 number of N atoms. d) 6.022 x 1023 number of N2molecules.
Ans: –
5) Convert into mole (AS-1)
a) 12g of O2 gas. b) 20g of water. c) 22g of carbon dioxide.
Ans: –
6) Write the valences of Fe in FeCl2 and FeCl3.
Ans: – The valences of Fe in FeCl2 are +2, and in FeCl3 is +3.
7) Calculate the molar mass of Sulphuric acid (H2SO4) and glucose (C6H12O6).
Ans: – H2SO4 molar mass= 2×1 + 32 + 16×4 =98.
C6H12O6 molar mass= 12×6 + 1×12 + 16×6 = 180.
8) Which has a greater number of atoms – 100g of sodium or 100g of iron? Justify your answer. (atomic mass of sodium = 23u, atomic mass of iron = 56u) (AS-1)
Ans: – No of atom in sodium is more than of the iron as the no of atom in 100g is denoted by (100/atomic no) ×6.023×10^23. So, we clearly see that the sodium has more numbers of atoms.
9) Fill the following table.
Ans: –
Sl no. |
Name | Symbol | Molar mass |
No of particles present in molar mass |
1 | Oxygen atom | O2 | 16 | 6.023×10^23 |
2 | Oxygen molecule | O | 8 | same |
3 | sodium | Na | 23 | same |
4 | Sodium ion | Na+ | 23 | same |
5 | Sodium chloride | NaCl | 47.5 | same |
6 | water | H2O | 18 | same |
10) Write an equation for decomposition reaction where energy is supplied in the form of Heat / light / electricity. (AS-1)
Ans: – Decomposition reaction is, 2AgIà2Ag + I2;
Silver iodide un presence of heat decompose into silver and iodine.
11) How chemical displacement reactions differ from chemical decompositionreaction? Explain with an example for each. (AS-1)
Ans: – The displacement and decomposition reaction are different as in decomposition reaction one compound breaks into different compounds or elements and in a displacement reaction the substrate is displaced from one to other molecules or form a new compound.
12) Name the reactions taking place in the presence of sunlight?
Ans: – The photochemical reaction happens in the presence of sunlight.
13) Give two examples for oxidation-reduction reaction. (AS-6)
Ans: – The reaction which is an example of oxidation is
CaH2 + O2 —> CaO + H2O;
The example of reduction reaction is, CuO + H2à Cu + H2O.
14) Draw the diagram to show the experimental setup to verify the law of conservation of mass. (AS-5)
Ans: –
Application of concepts
1) Why do we apply paint on iron articles? (AS-1)
Ans: – We always paint on the upper surface which is always in contact of air and light because after day by day open in air it reacts with the moisture and a brown layer is seen on its surface which known as rust.
2) What is the use of keeping food in air tight containers? (AS-6)
Ans: – The food always should be kept in air tight container as if it kept left behind the air then it gets oxidized by reaction with the moisture in air and become toxic. This phenomenon is known as the rancidity of food which we avoid by keeping it in air tight container.
Higher Order Thinking Questions
1) 15.9g. of copper sulphate and 10.6g of sodium carbonate react together to give 14.2g of sodium sulphate and 12.3g of copper carbonate. Which law of chemical combination is obeyed? How? (AS-1)
Ans: –
2) Carbon dioxide is added to 112g of calcium oxide. The product formed is 200g of calcium carbonate. Calculate the mass of carbon dioxide used. Which law of chemical combination will govern your answer? (AS-1)
Ans: –
3) Imagine what would happen if we do not have standard symbols for elements? (AS-2)
Ans: – If there is no such proper symbol of the elements then there will be various problem for the calculation of the characteristics of the element and as well as for keeping it in appropriate group of elements of same property will be hampered.
MULTIPLE CHOICE QUESTIONS
1.) Fe2O3 + 2Al —> Al2O3+ 2 Fe.
The above reaction is an example of:
a) Combination reaction b) Decomposition reaction c) Displacement reaction d) Double decomposition reaction.
Ans: – option (c).
2.) What happens when dil. hydrochloric acid is added to iron filings? Choose 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.
Ans: – option (a).
3.) 2 PbO(s) + C (s) —> 2Pb(s) + CO2 (g) [ ]
Which of the following statements are correct for the above chemical reaction?
a) Lead oxide is reduced b) Carbon dioxide is oxidized c) Carbon is oxidized d) (a) and (c) are correct.
Ans: – option (d)
4.) The chemical equation BaCl2 + Na2SO4 —> BaSO4 + 2NaCl represents following type of chemical reaction.
i) displacement ii) combination iii) decomposition iv) double-displacement.
Ans: – option (iv).
5.) The reaction of formation hydrogen chloride from hydrogen and chloridere presents following type of chemical reaction
i) decomposition ii) displacement, iii) combination iv) double-displacement.
Ans: – option (iii).