WBBSE Class 10 Physical Science Notes Chapter 3 Chemical Calculations | WBBSE Class 10 Physical Science Solutions Chapter 2 Notes in ENGLISH
WBBSE Class 10 Physical Science Chapter 3 Question Answer – Chemical Calculations
**Very Short Answer Type Questions:**
**Q1.** *What is the molecular weight of ammonium phosphate?*
**A1.** 149
**Q2.** *How much CaO is obtained from 10 kg CaCO3?*
**A2.** 5.6 kg
**Q3.** *How much CaCO3 will react with dil HCl to produce 22 g CO2?*
**A3.** 50 g
**Q4.** *How much hydrogen is required to produce 72 g water?*
**A4.** 8 g
**Q5.** *How much potassium chlorate is to be heated to produce as much oxygen as required to burn 6 g carbon completely?*
**A5.** 40.83 g
**Q6.** *How much quantity of silver chloride (AgCl) can be obtained from 1.0 g silver nitrate?*
**A6.** 0.844 g
**Q7.** *How many grams of limestone are needed to get 48g CO2?*
**A7.** 109.09 g
**Q8.** *How much hydrogen is produced when steam is passed over 28 kg red hot iron?*
**A8.** 1.33 kg
**Q9.** *What is mole number of a substance?*
**A9.** Mole number of a substance
**Q10.** *What is the percentage of water in blue vitriol?*
**A10.** 36.07%
**Q11.** *2 Mg + O2 = 2 MgO; what type of chemical reaction is it?*
**A11.** Direct combination type of chemical reaction.
**Q12.** *HCl + NaOH = NaCl + H2O; what type of chemical reaction is it?*
**A12.** Neutralization reaction.
**Q13.** *Zn + CuSO4 = ZnSO4 + Cu; what type of chemical reaction is it?*
**A13.** Substitution reaction.
**Q14.** *NH4 CNO (8) CO(NH2)2; what type of chemical reaction is it?*
**A14.** Rearrangement reaction.
**Q15.** *Give an example of double decomposition type of reaction.*
**A15.** AgNO3 + NaCl = AgCl + NaNO3
**Q16.** *State a limitation of a chemical equation.*
**A16.** A reaction, whether exothermic or endothermic, is not known from a chemical equation.
**Q17.** *Give an example of addition reaction.*
**A17.** Carbon monoxide reacts with chlorine to form carbonyl chloride (COCl2).
**Q18.** *Give an example of a substitution reaction.*
**A18.** Chlorine reacts with methane (CH4) to form successively CH3 Cl, CH2 Cl2, CHCl3, and ultimately CCl4.
**Q19.** *Give an example of a thermal decomposition type of reaction.*
**A19.** Calcium carbonate on heating decomposes into calcium oxide and carbon dioxide.
**Q20.** *Give an example of redox type of reaction.*
**A20.** [Not provided in the original text.]
**Q21.** *Balance the following reaction: Fe + H2O(Fe3O4 + H2.*
**A21.** Balanced equation: 3 Fe + 4 H2O = Fe3O4 + 4 H2
**Q22.** *2 SO2 + O2 ⇌ 2 SO3; what type of reaction is it?*
**A22.** Reversible type of reaction.
**Q23.** *A + B2+ = A2+ + B; what type of reaction is it?*
**A23.** Oxidation-reduction type of reaction.
**Q24.** *Balance the following reaction: MnO2 + HCl → MnCl2 + Cl2 + H2O.*
**A24.** Balanced equation: MnO2 + 4 HCl = MnCl2 + Cl2 + 2 H2O
**Q25.** *Balance the following reaction: Ag2SO4 + BaCl2 → BaSO4 + AgCl.*
**A25.** Balanced equation: Ag2SO4 + BaCl2 = BaSO4 + 2 AgCl
**Q26.** *Write the equation relating energy with mass.*
**A26.** E = mc^2
**Q27.** *Write the relation between molecular mass and vapor density.*
**A27.** Molecular mass = 2 × Vapor density.
**Q28.** *Calculate the vapor density of oxygen relative to hydrogen.*
**A28.** Vapor density of oxygen = Molecular mass of oxygen / 2 = 32 / 2 = 16
**Q29.** *6 g carbon on complete combustion produce how much volume of CO2 at STP?*
**A29.** 6 g carbon on complete combustion produces 11.2 L CO2 at STP.
**Q30.** *One mole of zinc reacts with excess H2SO4 to produce how many moles of hydrogen?*
**A30.** 1 mole of hydrogen.
**Short Answer Type Questions:**
**Q1.** *What is empirical formula?*
**A1.** Empirical formula: It is the formula of a compound that gives the simple whole number ratio of the atoms of various elements present in one molecule of the compound.
**Q2.** *What is molecular formula?*
**A2.** Molecular formula: It is the formula of a compound that gives the actual number of atoms of various elements present in one molecule of the compound.
**Q3.** *What are the limitations of chemical formula?*
**A3.** Limitations of chemical formula:
- It fails to convey whether the elements in a molecule are present in the form of atoms or ions.
- It does not tell anything about the binding force that holds atoms in a molecule together.
- It does not tell us about the arrangement of various atoms with respect to one another within the molecule.
**Q4.** *What is structural formula?*
**A4.** Structural formula: A formula that gives the actual arrangement of the different atoms in the molecule or shows how the different atoms in the molecule are linked together.
**Q5.** *What is the percentage of an element?*
**A5.** Percentage of an element: It is the number of parts by weight of it present in 100 parts by weight of the compound.
**Q6.** *What are mass-mass relationship problems?*
**A6.** Mass-mass relationship problems: In this type of problems, the mass of one of the reactants/products is to be calculated if that of the other reactants/products is given.
**Q7.** *What are mass-volume relationship problems?*
**A7.** Mass-volume relationship problems: In this type of problems, mass or volume of one of the reactants or products is calculated from the volume or mass of other
reactants or products by using the stoichiometry of the reaction.
**Q8.** *What are volume-volume relationship problems?*
**A8.** Volume-volume relationship problems: In this type of problems, the volume of one of the reactants/products is to be calculated if that of the other reactants/products is given.
**Q9.** *What is Avogadro's hypothesis?*
**A9.** Avogadro's hypothesis: Equal volumes of all gases under similar conditions of temperature and pressure contain an equal number of molecules.
**Q10.** *Define mole.*
**A10.** Mole: It is the amount of substance that contains the same number of chemical units (atoms, molecules, ions, etc.) as there are atoms in exactly 12 grams of pure carbon-12.
**Q11.** *Define molar volume.*
**A11.** Molar volume: It is the volume occupied by one mole of any (ideal) gas at standard temperature and pressure (STP), which is 22.4 L.
**Q12.** *What is Avogadro's number?*
**A12.** Avogadro's number: It is the number of atoms, ions, or molecules in one mole of a substance, which is approximately 6.022 x 10^23.
**Q13.** *What are the factors affecting the rate of chemical reactions?*
**A13.** Factors affecting the rate of chemical reactions:
- Nature of reactants
- Concentration of reactants
- Temperature
- Pressure
- Surface area
- Presence of catalyst
**Q14.** *What is activation energy?*
**A14.** Activation energy: The minimum energy required to initiate a chemical reaction.
**Q15.** *Define catalyst.*
**A15.** Catalyst: A substance that alters the rate of a chemical reaction without itself undergoing any permanent chemical change.
**Q16.** *What is homogeneous catalysis?*
**A16.** Homogeneous catalysis: Catalysis in which the catalyst is in the same phase as the reactants.
**Q17.** *What is heterogeneous catalysis?*
**A17.** Heterogeneous catalysis: Catalysis in which the catalyst is in a different phase from the reactants.
**Q18.** *What is the law of multiple proportions?*
**A18.** Law of multiple proportions: When two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in simple whole number ratios.
**Q19.** *What is the law of definite proportions?*
**A19.** Law of definite proportions: A chemical compound always contains the same elements in the same fixed proportions by mass, regardless of the source of the compound.
**Q20.** *What is the law of conservation of mass?*
**A20.** Law of conservation of mass: Mass can neither be created nor destroyed in a chemical reaction; it can only be rearranged.
**Q21.** *State and explain Gay-Lussac's law of combining volumes.*
**A21.** Gay-Lussac's law of combining volumes: When gases react together at constant temperature and pressure, the volumes of the reacting gases (and also of the gaseous products formed, if gaseous) bear a simple ratio to one another.
**Q22.** *What is STP?*
**A22.** STP: Standard temperature and pressure. For gases, it is defined as 0 degrees Celsius (273.15 K) and 1 atmosphere pressure.
**Q23.** *What are real gases?*
**A23.** Real gases: Gases that do not strictly follow the ideal gas law, especially at high pressure and low temperature.
**Q24.** *What is the ideal gas law?*
**A24.** Ideal gas law: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.
**Q25.** *What is Graham's law of diffusion?*
**A25.** Graham's law of diffusion: The rate of diffusion of a gas is inversely proportional to the square root of its density or molar mass.
**Q26.** *What is Dalton's law of partial pressures?*
**A26.** Dalton's law of partial pressures: In a mixture of non-reacting gases, the total pressure exerted by the mixture is equal to the sum of the partial pressures of individual gases.
**Q27.** *Define the term 'standard hydrogen electrode'.*
**A27.** Standard hydrogen electrode: The standard hydrogen electrode (SHE) is a redox electrode that forms the basis of the thermodynamic scale of oxidation-reduction potentials.
**Q28.** *What is corrosion?*
**A28.** Corrosion: The deterioration of a metal due to a reaction with its environment.
**Q29.** *What is electroplating?*
**A29.** Electroplating: The process of depositing a thin layer of metal on an object for decorative or functional purposes.
**Q30.** *Define fuel.*
**A30.** Fuel: A substance that reacts with oxygen to release energy in the form of heat or light.
**Long Answer Type Questions:**
**Q1.** *Explain the laws of chemical combination.*
**A1.** Laws of chemical combination:
1. **Law of conservation of mass:** Mass can neither be created nor destroyed in a chemical reaction; it can only be rearranged.
2. **Law of definite proportions:** A chemical compound always contains the same elements in the same fixed proportions by mass, regardless of the source of the compound.
3. **Law of multiple proportions:** When two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in simple whole number ratios.
**Q2.** *Explain the concept of limiting reactant with an example.*
**A2.** Limiting reactant: The limiting reactant is the reactant that is completely consumed in a chemical reaction, determining the amount of product formed.
Example:
Consider the reaction: \(2 H_2 (g) + O_2 (g) \rightarrow 2 H_2 O (g)\)
Suppose we have 4 moles of \(H_2\) and 2 moles of \(O_2\). The balanced equation tells us that the ratio of \(H_2\) to \(O_2\) is 2:1. However, since we only have 2 moles of \(O_2\), it will be completely consumed, and only 4 moles of \(H_2\) will react.
\(H_2\) is the limiting reactant in this case because it determines the maximum amount of product that can be formed.
**Q3.** *Describe the various factors affecting the rate of chemical reactions.*
**A3.** Factors affecting the rate of chemical reactions:
1. **Nature of reactants:** Different substances react at different rates. For example, a reaction involving breaking strong bonds may be slower than a reaction where weaker bonds are broken.
2. **Concentration of reactants:** An increase in the concentration of reactants generally leads to an
