Selina Concise Class 8 Chemistry Solution Chapter No. 5- ‘Language of Chemistry’ For ICSE Board Students.
1)
a)
Answer : Radical :
Radical is an atom or molecules that contain unpaired electrons or charge on it that is negative or positive charge .
b)
Answer: Valency
One elements has the power or capacity to form a bond with another elements or atom for the formation of compound , this capacity or power is known as Valency.
c)
Answer : Molecular formula :
The number and atom present or consists of a symbolically in a chemical compound is known as Molecular formula.
2)
a)
Answer : Hydroxide :
- Symbol : OH–
- Valency : 1 (Monovalent)
- Hydroxide is a negative radical
b)
Answer : Chloride:
- Symbol : Cl–
- Valency : 1 (Monovalent)
- Chloride is a negative radical
c)
Answer : Carbonate :
- Symbol : CO2-
- Valency : 2 (Bivalent)
- Carbonate is a negative radical
d)
Answer : Ammonium :
- Symbol : NH+
- Valency : 1 (Monovalent)
- Ammonium is a positive radical
e)
Answer : Nitrate :
- Symbol : NO3–
- Valency : 1 (Monovalent )
- Nitrate is a negative radical.
4.).
a).
Answer : Baking soda :
- Baking soda also known as sodium bicarbonate
- Formula of baking soda is Na2CO3
- Elements present in baking soda , sodium, carbon, and oxygen.
b) .
Answer : Common salt :
- Chemical name of common salt is sodium chloride.
- Molecular formula of common salt is NaCl.
- Elements present in common salt is , sodium and chlorine.
c.).
Answer : Sulphuric acid
- Molecular formula of sulphuric acid is H2SO4
- Elements present in the sulphuric acid is , Hydrogen, sulphur , Oxygen.
d.).
Answer : Nitric Acid
- Molecular formula of Nitric Acid is HNO3
- Elements present in the Nitric Acid is , Nitrogen , Hydrogen , And oxygen.
5.) .
a) .
Answer : Aluminium Chloride (AlCl3 ) :
- The Valency of aluminium (Al3+) is 3.
- Chloride ( Cl3-) radical present in compound aluminium chloride.
- The valence of Chloride radical is 1 (Monovalent ).
b) .
Answer: Aluminium oxide ( Al2O3):
- The Valency of aluminium (Al3+) is 3.
- Oxide ( O2-) radical present in compound aluminium oxide.
- The valence of oxide is 2 (Bivalent ).
c.) .
Answer : Aluminium Nitride ( Al N)
- The Valency of aluminium (Al3+) is 3.
- Nitride ( N3-) radical present in compound aluminium nitride.
- The valence of nitride radical is 3 (trivalent ).
d.) .
Answer : Aluminium sulphate Al2(SO4)3
- The Valency of aluminium (Al3+) is 3.
- Sulphate ( SO42-) radical present in compound aluminium sulphate.
- The valence of sulphate radical is 2 (bivalent ).
6).
Answer : Variable Valency :
The elements have different capacities or Valency or more than one Valency are called variable Valency .
Example : 1) Copper ( Cu) :
- Copper have lower Valency state Cu + or Cu(I) Cuprousis one.
- Copper have higher Valency state Cu 2+ or Cu(II) Cupric is 3 .
2.) . Iron ( Fe) :
- Iron have lower Valency state Fe2+ or Fe(III) Ferrous is 2
- Iron have higher Valency state Fe3+ or Fe (III) Ferric is 3.
7).
a) .
Answer : Chemical equation :
Showing or describing the elements or compound by symbolically, and formulas , which is chemically react each other and form new compound is known as chemical equation.
b) .
Answer: It is necessary to balance chemical equation because it show us both side that is reactant and the product mass of constituents or compound is same in the chemical equation during the chemical reaction., according to the law of conservation state mass can neither be The elements have different capacities or Valency or more than one Valency are called variable Valency . nor be destroyed. It is only swipe or rearrangement of atom.
c.) .
Answer : limitations :
- It does not reveal or not informed about the physical state of reactant or product.
- It doesn’t inform about the rate of reaction how fast or slow it.
- It doesn’t give information about the condition of reaction such as pressure temperature .
- Chemical reaction do not tell about time needed for the completion of reaction.
- It doesn’t provide the information about the concentration reactant and product.
8).
Answer : Many ways that can be made chemical equation informative that is following .
- Chemical equation provide us information about the physical state of reactant or product that it indicates solid (s) , liquid (l) and gas for (g) and up arrow () and precipitation indicated by down arrow ( ).
- Indicating change of heat In a chemical reaction.
Example : C + O₂ → CO₂ + heat
- Heat is Indicating by delta ∆ the which condition reaction takes place ,on the arrow(→ ) of the reaction.
- Indicate reversible reaction by the arrow (⇌).
9).
Answer : State the law of conservation of mass :
Statement of law of conservation mass is that matter can neither be created nor be destroyed it only change on form to another. It means mass of the substance or molecule that take part in chemical reaction is same or equal both side reactant or product side.
10).
a) .
Answer:
Sr. No. | Reactant | Product |
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 .
|
b) .
Answer:
Sr. No. | Balance Chemical equation | Unbalance 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 unbalance chemical equation. |
2 | Balance chemical equation follow the law of conservation of mass . | Unbalance 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. |
11) .
a)
Answer : N₂ + H₂ → NH ₃
- Reactant are nitrogen and hydrogen , product Is ammonia .
Reactant .
Nitrogen = 2
Hydrogen = 2
Product .
Nitrogen= 1
Hydrogen = 3
- We can balance this equation by multiplying hydrogen by 3 on reactant side.
- And multiply by 2 on product side
- The balance chemical equation Is
N₂ + 3H₂ → 2 NH ₃
Reactant = Product
Nitrogen = 2 Nitrogen =2
Hydrogen = 5 Hydrogen=5
b) .
Answer : H₂ + O₂ → H₂O
- Reactant are Hydrogen and Oxygen and product Is water.
Reactant.
Hydrogen = 2
Oxygen = 2
Product.
Hydrogen = 2
Oxygen = 1
- We can balance this equation by multiplying the hydrogen reactant sideby 2.
- And multiply the product by two(2).
- The balance chemical equation Is
2 H₂ + O₂ → 2 H₂O
Reactant = Product
Hydrogen = 4 Hydrogen =4
Oxygen = 2 Oxygen =2
c) .
Answer : Na₂O + H₂O → NaOH
- Sodium react with cold water to gives sodium hydroxide
- Reactant are sodium, hydrogen and oxygen and product Is sodium hydroxide.
Reactant.
Sodium = 2
Hydrogen = 2
Oxygen = 2
Product.
Sodium = 1
Hydrogen = 1
Oxygen = 1
- We can balance this equation by multiplying the product by 2.
- The balance chemical equation Is.
Na₂ + H₂O → 2 NaOH
Reactant = Product
Sodium =2 Sodium = 2
Hydrogen = 2 hydrogen =2
Oxygen = 2 oxygen =2
d) .
Answer : Zn + HCl → ZnCl₂ + H₂
- Zinc Is react with hydrochloric acid to zinc chloride and hydrogen gas Is evolved.
- Reactant are zinc hydrogen and chlorine and product Is zinc chloride and hydrogen gas .
Reactant.
Zinc = 1
Hydrogen = 1
Chlorine = 1
Product.
Zinc = 1
Hydrogen = 2
Chlorine = 2
- We can balance this equation by multiplying the hydrochloric acid In a reactant side by 2.
- Balance chemical equation Is
Zn + 2HCl → ZnCl₂ + H₂
Reactant = Product
Zinc = 1 Zinc = 1
Hydrogen = 2 hydrogen =2
Chlorine = 2 Chlorine = 2
12).
a) .
Answer : Word equation :
Iron + Chlorine → Iron(III) chloride
Chemical equation :
2Fe + 3Cl₂ → 2FeCl₃
b) .
Answer : Word equation :
Magnesium + dil. sulphuric acid →magnesium sulphate + hydrogen
Chemical equation :
Mg(s) + H2SO4(dil.) → MgSO4(aq.)+H2(g)
c ) .
Answer : Word equation :
Magnesium + Oxygen→Magnesium Oxide
Chemical equation :
2Mg (s) + O₂ (g) → 2MgO (s)
d.)
Answer : Word equation :
Calcium oxide + Water→Calcium Hydroxide
Chemical equation :
CaO + H₂O → Ca(OH)₂
e.) .
Answer : Word equation :
Sodium + Chlorine → Sodium chloride
Chemical equation :
2 Na (s) + Cl 2 (g) → 2 NaCl (s)
13).
Answer : Zn (s) + HCl (dil.) → ZnCl₂ (aq.) + H₂(g)
From above reaction we will get the information that it is a single displacement reaction in which Zinc metal in a solid state react with dilute hydrochloric acid , in here hydrogen is displace by zinc metal and form Hydrogen gas and zinc chloride which is salt in a aqueous state.