Allied solutions simplified middle school chemistry class 8 Solutions for Chapter 5 language of chemistry

Q1) Explain the term ‘symbol’. State a reason why - the symbol of calcium is ‘Ca’ & of copper is ‘Cu’

Q2) Define the term ‘valency’. With reference to water & ammonia as compounds respectively, state the valency of oxygen & nitrogen. Magnesium [[2, 8, 2]] has valency 2+. Give reasons.

Q3) Explain the term ‘variable valency’. Copper having electronic configuration [[2,8,18,1]] exhibits variable valency. Give a reason for the same & name the compound CuCl & CuCl_2

Q4) State the valencies of the following metallic elements -

(a) Potassium

(b) Sodium

(c) Calcium

(d) Magnesium

(e) Zinc

(f) Aluminium

(g) Chromium

Q4) Certain metals exhibit variable valencies which include valencies: 1+, 2+, 3+ & 4+. State the variable valency of the following metals -

(a) Copper

(b) Silver

(c) Mercury

(d) Iron

(e) Tin

(f) Lead

Q6) State which of the following ions or radicals given below of non-metallic elements exhibit valency: 1- , 2- & 3-

(a) Chloride

(b) Bromide

(c) Iodide

(d) Nitrate

(e) Hydroxide

(f) Bicarbonate

(g) Bisulphite

(h) Bisulphate

(i) Aluminate

(j) Permanganate

(k) Oxide

(l) Sulphide

(m) Sulphite

(n) Sulphate

(o) Carbonate

(p) Dichromate

(q) Zincate

(r) Plumbite

(s) Phosphate

(t) Nitride

Q7) Differentiate between the terms - ‘ion’ & ‘radical’ with suitable examples.

Q8) Write the chemical formula of the following compounds in a step by step manner -

(a) Potassium Chloride

(b) Sodium Bromide

(c) Potassium Nitrate

(d) Calcium Hydroxide

(e) Calcium Bicarbonate

(f) Sodium Bisulphate

(g) Potassium sulphate

(h) Zinc Hydroxide

(i) Potassium permanganate

(j) Potassium dichromate

(k) Aluminium Hydroxide

(l) Magnesium nitride

(m) Sodium zincate

(n) Copper [[II]] oxide

(o) Copper [[I]] sulphide

(p) Iron [[III]] chloride

(q) Iron [[II]] hydroxide

(r) Iron [[III]] sulphide

(s) Iron [[III]] oxide

Q9) What is a chemical equation? How is it represented. Differentiate between a ‘word equation’ and a ‘molecular equation’ with a suitable example.

Q10) State the information provided by a chemical equation. Chemical equations suffer from a number of limitations. State the main limitations of a chemical equation.

Q11) State what is a balanced equation with a relevant example. Give a reason why an equation is balanced with reference to the law of conservation of matter.

Q12) Write a balanced molecular equations for the word equations:

1. Calcium + Oxygen → Calcium oxide

2. Calcium + Water → Calcium hydroxide + Hydrogen

3. Zinc + Sulphuric acid → Zinc sulphate + Hydrogen

4. Lead sulphate + Ammonium hydroxide → Ammonium Sulphate + Lead hydroxide

5. Copper hydroxide + Nitric acid → Copper nitrate + Water

6. Lead nitrate + Sodium Chloride → Sodium Nitrate + Lead Chloride

Q13) Balance the following equations:

(a) P+O_2\ →\ P_2O_5

(b) Na_2O\ +\ H_2O\ →\ NaOH

(c) K\ +\ H_2O\ →\ KOH\ +\ H_2

(d) Fe\ +\ H_2O\ →\ Fe_3O_4\ +\ H_2

(e) CaO\ +\ HCl\ →\ CaCl_2\ +\ H_2O

(f) Fe\ +\ Cl_2\ →\ FeCl_3

(g) Al\ +\ H_2O\ →\ Al_2O_3\ +\ H_2

(h) Al\ +\ H_2SO_4\ →\ Al_2\left(SO_4\right)_{3\ }+\ H_2

(i) Fe_2O_3\ +\ H_2\ →\ Fe\ +\ H_2O

(j) C\ +\ H_2SO_4\ →\ CO_2\ +\ H_2O\ +\ SO_2

(k) Pb_3O_4\ →\ PbO\ +\ O_2

(l) Al\ +\ O_2\ →\ Al_2O_3

(m) NO\ +\ O_2\ \ →\ NO_2

(n) ZnS\ +\ O_2\ \ →\ ZnO\ +\ SO_2

(o) Pb_3O_4\ +\ HCl\ \ →\ PbCl_2+\ H_2O\ +\ Cl_2

(p) ZnO\ +\ NaOH\ \ →\ Na_2ZnO_2\ +\ H_2O

(q) H_2S\ +\ Cl_2\ →\ S\ +\ HCl

(r) FeCl_3\ +\ NaOH\ →\ NaCl\ +\ Fe\left(OH\right)_3

(s) Fe_2O_3\ +\ CO\ →\ Fe\ +\ CO_2

(t) KHCO_3\ →\ K_2CO_2\ +\ H_2O\ +\ CO_2

(u) CuO\ +\ NH_3\ →\ Cu\ +\ H_2O\ +\ N_2

Q1) Complete the statements given below by filling in the blank with the correct words.

1. The formula of silver I chloride is _____ [AgCl/AgCl_2]
2. The basic unit of an element is a/an _____ [[molecule/atom/ion]]
3. Atom contains _____ [[netron/nucleus]] with positively charged ________ [[electrons/protons]]
4. Element _______ [[calcium/lead/carbon]] has the symbol derived from its latin 'plumbum'.
5. From the elements - He, Br, Pt, & O; the element which forms a polyatomic molecule is _____ & which is liquid at room temperature is ____.
6. The valency of iron in FeO is _____ [[2+/1+]] of chlorine [[chloride]] in CaCl_2 is ________ [[1-/2-]] and of dichromate in K_2Cr_2O_7 is ______ [[2+/2-]]

Q2) Match the statements - 1 to 10 below with their correct answers from - A to J

Q3) Match the compounds in List I - 1 to 20 with their correct formulas in list II - A to T

Q4) Underline the incorrectly balanced compound in each equation & rewrite the correct equation:

1. 2Na+3H_2O\ →\ 2NaOH+H_2
2. 4P+4O_{2\ \ }→\ 2P_2O_5
3. Fe_2O_3+2H_2\ →\ 2Fe\ +\ 3H_2O
4. 2Al+2H_2SO_4\ →\ Al_2(SO_4)_3+3H_2
5. N_2+3H_2\ →\ NH_3
6. ZnO+3NaOH\ →\ Na_2ZnO_2+H_2O
7. FeCl_3+3NH_4OH\ →\ 2NH_4Cl+Fe(OH)_3
8. FeS+2HCl\ →\ 2FeCl_2+H_2S
9. 3NH_3+H_2SO_4\ →\ (NH_4)_2SO_4
10. PbO_2+4HCl\ →\ PbCl_2+H_2O+Cl_2