Selina Concise Class 7 Chemistry Solution Chapter No. 5- ‘Language of Chemistry’ For ICSE Board Students.
1)
a)
Answer : Chemical reaction :
A compound or molecules (Reactant) chemically react with each other and form one or more new different compound or substance ( product) are known as chemical reaction.
b)
Answer : Chemical equation :
Showing or describing the elements or compound by symbol , and formulas , which is chemically react each other and form new compound is known as chemical equation.
c)
Answer : We need to balance chemical equation because it show us, equal mass of constituents or quantity of component and equal number of atoms is same in both side that is reactant and product side in the chemical equation during the chemical reaction.
2)
Answer : necessary condition for chemical reaction takes place are following .
- Mixing of components.
- Solution of the substance .
- Catalyst .
- Pressure.
- Heat and energy .
3)
a)
Answer :
Sr.No | Reactants | Products |
1. | Chemical equation or reaction Start from a Compound or Substance are called Reactant . | Chemical reaction give the compound or substance at end or as a result such compounds or substance known as product . |
2 | Reactant present in the start of the reaction . | Product get at the end of the reaction .
|
3. | Example
2H₂ + O₂ → 2 H₂O In this reaction hydrogen and oxygen are reactant . |
Example :
2H₂ + O₂ → 2 H₂O In this reaction H2O ( water ) is a product .
|
Sr.No | Chemical reaction | Chemical equation |
1. | A compound or molecules ( Reactant ) chemically react with each other and form one or more new different compound or substance ( product) are known as chemical reaction . | Showing or describing the elements or compound by symbol , and formulas , which is chemically react each other and form new compound is known as chemical equation.
|
2 | Chemical reaction Is a process to change reactant into a new substance known as product. | Chemical equation is represented chemical reaction |
3 | For example Hydrogen gas combine with oxygen gas to produce Water . | Example :
2H₂ (g) + O₂(g) →2H₂O(l) |
Sr.No | Balance chemical equation | Skeletal chemical equation |
1 | In chemical equation number of molecules or atom is same in both side that is reactant side and product side , are known as balance Chemical equation. | In chemical equation number of molecules or atom is not same in both side that is reactant side and product side, are known as Skeletal chemical equation. |
2 | Balance chemical equation follow the law of conservation of mass . | Skeletal chemical equation does not follow the law of conservation of mass. |
3 | Example
2 H₂ + O₂ → 2 H₂O In this reaction hydrogen and oxygen are in same number in both side that is reactant and product side. |
Example :
H₂ + O₂ → H₂O In this reaction hydrogen and oxygen are not in same number in both side that is reactant and product side. |
4)
a)
Answer : Potassium chlorate →. Potassium chloride + Oxygen
2KClO₃ → 2KCl + 3O₂
b)
Answer : Zinc. +. Hydrogen chloride (dil.) → Zinc chloride + hydrogen (gas)
Zn + 2HCl → ZnCl₂ + H₂
c)
Answer : Ferrous chloride ( Iron(II) Chloride) + Chlorine → Ferric chloride ( iron (III) Chloride)
2FeCl₂ + Cl₂ → 2FeCl₃
d)
Answer :. Carbon monoxide → Carbon dioxide
2CO + O₂ → 2CO₂
e)
Answer : Calcium + Oxygen → Calcium oxide
2Ca + O₂ → 2CaO
f)
Answer : Sodium + Oxygen → Sodium Oxide
4Na + O₂ → 2Na₂O
g)
Answer : Sodium Hydroxide + Sulphuric acid → Sodium Sulphate + Water
2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
h)
Answer :. Silver Bromide → Silver + Bromine
2AgBr → 2Ag + Br₂
i)
Answer : Potassium Nitrate → Potassium Nitride + Oxygen
2KNO₃ → 2KNO₂ + O₂
5)
a)
Answer : FeS + 2HCl → FeCl₂ + H₂S
b)
Answer : Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
c)
Answer : 2H₂ + O₂ → 2H₂O
d)
Answer : Na₂O + H₂O → 2NaOH
6)
Answer : H₂ + Cl₂ → 2HCl
Hydrogen chlorine hydrogen chloride (Hydrochloric acid)
• When hydrogen and chlorine molecules are reactant which is in gas form .
• When Hydrogen and Chlorine molecules chemically react with each other to form product Hydrogen chloride
• Hydrogen chloride also known as hydrochloric acid.
7) .
a) .
Answer : When sugar give heat to form black solid substance as a residue known as charcoal and water vapour .
b) .
Answer : Manganese dioxide added as catalyst in a potassium chlorate and give heat , decomposition reaction occur potassium chlorate produced potassium chloride and oxygen .
c)
Answer :When dilute Acetic acid is poured in baking soda or sodium bicarbonate it produced effervescence of carbon dioxide gas , sodium acetate and water .
d)
Answer : When aqueous solution of sodium chloride mixed with an aqueous solution of silver nitrate to produce white Precipitate of silver chloride and sodium nitrate formed.
e)
Answer : When ammonium chloride is heated with sodium hydroxide to produce strong pungent smell gas of ammonia and formed sodium chloride solution and water .
f)
Answer : When water is added to quick lime or calcium oxide to produce calcium hydroxide along with large amount of heat energy evolved.
8)
a)
Answer : Calcium carbonate →. Calcium oxide +. Carbon dioxide
CaCO₃ → CaO + CO₂
b)
Answer : Carbon + Oxygen →. Carbon dioxide
C + O ₂ → CO₂
c)
Answer : Calcium oxide + Water → Calcium hydroxide
CaO + H₂O → Ca(OH)₂
d)
Answer : Aluminium. +. Chlorine. →. Aluminium chloride
2Al + 3Cl₂ → 2AlCl₃
e)
Answer : Iron. +. Sulphur. →. Iron sulphide
Fe + S → FeS
f)
Answer : Sodium carbonate +Hydrochloric acid ( dil.) →. Sodium chloride + water + carbon dioxide
Na₂CO₃ + 2HCl (dil) → 2NaCl + H₂O + CO₂
g)
Answer : Barium chloride. + Sodium sulphate →. Barium Sulphate. + Sodium chloride
BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
h)
Answer : iron sulphide + Hydrochloric acid (dil.) → iron(II) chloride + hydrogen Sulphate
FeS + 2 HCl (dil.) → FeCl₂ + H₂S
i)
Answer : Calcium + water → Calcium hydroxide
Ca + 2H₂O → Ca(OH)₂ + H₂
OBJECTIVE TYPE QUESTIONS
1)
a) The substance which undergo chemical change are called ………….
Answer : Reactant
(Chemical equation or reaction Start from a Compound or which undergo chemical reaction known as called Reactant.)
b) The substances formed as result of a chemical reaction are called ………..
Answer : Produce
(Chemical reaction give the compound or substance at end or as a result such compounds or substance known as product)
c) During a chemical reaction transfer of …………. Takes place.
Answer : energy
(During a chemical reaction , reactant bond break down and rearrangement of atoms takes place and energy is stored in the form of bond in compound , So energy is transferred during chemical reaction)
d) The basic condition necessary for chemical reaction is …………..
Answer : close contact .
(In a chemical reaction two molecules come together and colloid or mix together to form a new substance or compound that is why close contact is the basic condition necessary for chemical reaction)
e) In some chemical reaction an insoluble………is formed when two solution is mixed.
Answer : Precipitate
(When chemical reaction occur new substance are formed which is solid substance or insoluble in a liquid known as precipitate )
2)
a)
Answer : False
b)
Answer : True
c)
Answer : False
d)
Answer : True
e)
Answer : False
MULTIPLE CHOICE QUESTIONS
1)
Answer : a) Symbol and formulae
(Chemical equation is described by Showing the elements or compound by symbol , and formulas , which is chemically react each other and form new compound )
2)
Answer : a) Law of conservation of mass
(Balancing chemical equation follow the state of law of conservation of mass, according to the law of conservation of mass , mass can neither be nor be destroyed. It is only swipe or rearrangement of atom so due to this reactants and products mass are equal.
3)
Answer : c) black
(Copper carbonate is heated it gives
4)
Answer : b) Yellow
(When potassium iodine solution mixed with lead acetate solution it produced yellow precipitation of lead iodine and potassium acetate formed)
5)
Answer : c) Hydrogen Sulphide
(Hydrogen sulphide has a characteristic colourless, flammable gas, rotten egg smell )
6)
Answer : a) Carbon dioxide
(When sodium carbonate react with dilute hydrochloric acid to produced sodium chloride , Water and Effervescences of carbon dioxide gas evolved).