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THE LANGUAGE OF CHEMISTRY - Q&A

EXERCISE 1 (A)

1. What is a symbol? What information does it convey?
A symbol is the short form that stands for the atom of a specific element or the abbreviation used for the name of an element.
It conveys the following information:
1. It represents a specific element.
2. It represents one atom of that element.
3. It represents the atomic weight of the element (mass of one atom).

2. Why is the symbol S for sulphur, but Na for sodium and Si for silicon?
The symbol S is used for Sulphur because it is the first letter of its English name.
However, when the first letter of more than one element is the same (e.g., Sulphur, Sodium, Silicon all start with 'S'), two letters are used. For Sodium, the symbol 'Na' is derived from its Latin name "Natrium". For Silicon, the symbol 'Si' is derived from the first two letters of its English name to distinguish it from Sulphur.

3. If the symbol for Cobalt, Co, were written as CO, what would be wrong with it?
If Cobalt were written as CO, it would represent a molecule of the compound Carbon Monoxide (containing one Carbon atom and one Oxygen atom) rather than an atom of the element Cobalt. In a symbol, the second letter must always be small (lowercase) to indicate it belongs to the same element.

4. What do the following symbols stand for?
(a) H
(b) H₂
(c) 2H
(a) H stands for one atom of the element Hydrogen.
(b) H₂ stands for one molecule of Hydrogen (containing 2 atoms).
(c) 2H stands for two separate atoms of Hydrogen.

5. (a) Explain the terms 'valency' and 'variable valency'.
(b) How are the elements with variable valency named? Explain with an example.
(a) Valency: It is the combining capacity of an atom of an element. It is defined as the number of hydrogen atoms that combine with or displace one atom of that element. Alternatively, it is the number of electrons lost, gained, or shared by an atom during a chemical reaction.
Variable Valency: Certain elements exhibit more than one valency in different compounds. This phenomenon is called variable valency (e.g., Iron shows valency 2 and 3).

(b) Elements with variable valency are named using suffixes or Roman numerals:
1. Suffix method: The suffix "-ous" is used for the lower valency and "-ic" for the higher valency.
2. Roman Numeral method: The valency is written in Roman numerals in brackets after the name of the metal.
Example: Iron exhibits valencies 2 and 3.
- Fe²⁺ is named Ferrous or Iron(II).
- Fe³⁺ is named Ferric or Iron(III).

6. Give the formula and valency of:
(a) aluminate
(b) chromate
(c) aluminium
(d) cupric
(a) Aluminate: Formula: AlO₂^1-, Valency: 1
(b) Chromate: Formula: CrO₄^2-, Valency: 2
(c) Aluminium: Symbol: Al³⁺, Valency: 3
(d) Cupric: Symbol: Cu²⁺, Valency: 2

7. What is a chemical formula? What is the rule for writing a formula correctly?
A chemical formula is the symbolic representation of a molecule of a substance (element or compound). It denotes the number of atoms of each element present in one molecule.

Rule (Criss-Cross Method):
1. Write the symbols of the basic radical (positive ion) and acidic radical (negative ion) side by side.
2. Write the valency of each radical on top of its symbol.
3. Divide the valency numbers by their highest common factor (H.C.F.) to get a simple ratio.
4. Interchange the valencies and write them as subscripts to the right of the symbols. (Ignore '1').

8. What do you understand by the following terms?
(a) Acid radical
(b) Basic radical
(a) Acid radical: The electronegative radical (anion) contributed by an acid in the formation of a salt is called an acid radical. E.g., Chloride (Cl^-) in NaCl.
(b) Basic radical: The electropositive radical (cation) contributed by a base in the formation of a salt is called a basic radical. E.g., Sodium (Na⁺) in NaCl.

9. Match the following:
(a) Boric acid — (xvi) H₃BO₃
(b) Phosphoric acid — (xvii) H₃PO₄
(c) Nitrous acid — (xv) HNO₂
(d) Nitric acid — (xiv) HNO₃
(e) Sulphurous acid — (xiii) H₂SO₃
(f) Sulphuric acid — (xviii) H₂SO₄
(g) Hydrochloric acid — (xii) HCl
(h) Silica (sand) — (ii) SiO₂
(i) Caustic soda — (i) NaOH
(j) Caustic potash — (iv) KOH
(k) Washing soda — (iii) Na₂CO₃
(l) Baking soda — (vi) NaHCO₃
(m) Lime stone — (v) CaCO₃
(n) Water — (viii) H₂O
(o) Hydrogen sulphide — (vii) H₂S
(p) Ammonia — (xi) NH₃
(q) Phosphine — (ix) PH₃
(r) Methane — (x) CH₄

10. Select the basic and acidic radicals in the following compounds.
(a) MgSO₄
(b) (NH₄)₂SO₄
(c) Al₂(SO₄)₃
(d) ZnCO₃
(e) Mg(OH)₂
(a) Basic: Mg²⁺ (Magnesium), Acidic: SO₄^2- (Sulphate)
(b) Basic: NH₄⁺ (Ammonium), Acidic: SO₄^2- (Sulphate)
(c) Basic: Al³⁺ (Aluminium), Acidic: SO₄^2- (Sulphate)
(d) Basic: Zn²⁺ (Zinc), Acidic: CO₃^2- (Carbonate)
(e) Basic: Mg²⁺ (Magnesium), Acidic: OH^- (Hydroxide)

11. The valency of an element A is 3 and that of element B is 2. Write the formula of the compound formed by the combination of A and B.
Using the criss-cross method:
Element A valency: 3
Element B valency: 2
Interchanging valencies: A₂B₃
Formula: A₂B₃

12. Write chemical formula of the sulphate of Aluminium, Ammonium and Zinc.
1. Aluminium Sulphate: Al is 3+, Sulphate is SO₄^2-. Cross valencies: Al₂(SO₄)₃
2. Ammonium Sulphate: NH₄ is 1+, Sulphate is SO₄^2-. Cross valencies: (NH₄)₂SO₄
3. Zinc Sulphate: Zn is 2+, Sulphate is SO₄^2-. Ratio 2:2 simplifies to 1:1. Formula: ZnSO₄

13. Write the chemical names of the following compounds:
(a) Ca₃(PO₄)₂
(b) K₂CO₃
(c) K₂MnO₄
(d) Mn₃(BO₃)₂
(e) Mg(HCO₃)₂
(f) Na₄Fe(CN)₆
(g) Ba(ClO₃)₂
(h) Ag₂SO₃
(i) (CH₃COO)₂Pb
(j) Na₂SiO₃
(a) Calcium phosphate
(b) Potassium carbonate
(c) Potassium manganate
(d) Manganese borate
(e) Magnesium bicarbonate (or Magnesium hydrogen carbonate)
(f) Sodium ferrocyanide
(g) Barium chlorate
(h) Silver sulphite
(i) Lead acetate
(j) Sodium silicate

EXERCISE 1 (B)

1. Balance the following equations:

(a) Fe + H₂O → Fe₃O₄ + H₂
Balanced: 3Fe + 4H₂O → Fe₃O₄ + 4H₂

(b) Ca + N₂ → Ca₃N₂
Balanced: 3Ca + N₂ → Ca₃N₂

(c) Zn + KOH → K₂ZnO₂ + H₂
Balanced: Zn + 2KOH → K₂ZnO₂ + H₂

(d) Fe₂O₃ + CO → Fe + CO₂
Balanced: Fe₂O₃ + 3CO → 2Fe + 3CO₂

(e) PbO + NH₃ → Pb + H₂O + N₂
Balanced: 3PbO + 2NH₃ → 3Pb + 3H₂O + N₂

(f) Pb₃O₄ → PbO + O₂
Balanced: 2Pb₃O₄ → 6PbO + O₂

(g) PbS + O₂ → PbO + SO₂
Balanced: 2PbS + 3O₂ → 2PbO + 2SO₂

(h) S + H₂SO₄ → SO₂ + H₂O
Balanced: S + 2H₂SO₄ → 3SO₂ + 2H₂O

(i) S + HNO₃ → H₂SO₄ + NO₂ + H₂O
Balanced: S + 6HNO₃ → H₂SO₄ + 6NO₂ + 2H₂O

(j) MnO₂ + HCl → MnCl₂ + H₂O + Cl₂
Balanced: MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂

(k) C + H₂SO₄ → CO₂ + H₂O + SO₂
Balanced: C + 2H₂SO₄ → CO₂ + 2H₂O + 2SO₂

(l) KOH + Cl₂ → KCl + KClO + H₂O
Balanced: 2KOH + Cl₂ → KCl + KClO + H₂O

(m) NO₂ + H₂O → HNO₂ + HNO₃
Balanced: 2NO₂ + H₂O → HNO₂ + HNO₃

(n) Pb₃O₄ + HCl → PbCl₂ + H₂O + Cl₂
Balanced: Pb₃O₄ + 8HCl → 3PbCl₂ + 4H₂O + Cl₂

(o) H₂O + Cl₂ → HCl + O₂
Balanced: 2H₂O + 2Cl₂ → 4HCl + O₂

(p) NaHCO₃ → Na₂CO₃ + H₂O + CO₂
Balanced: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

(q) HNO₃ + H₂S → NO₂ + H₂O + S
Balanced: 2HNO₃ + H₂S → 2NO₂ + 2H₂O + S

(r) P + HNO₃ → NO₂ + H₂O + H₃PO₄
Balanced: P + 5HNO₃ → 5NO₂ + H₂O + H₃PO₄

EXERCISE 1 (C)

1. Fill in the blanks:
(a) Dalton used symbol circle [O] for oxygen circle with a dot for hydrogen.
(b) Symbol represents one atom(s) of an element.
(c) Symbolic expression for a molecule is called chemical formula (or molecular formula).
(d) Sodium chloride has two radicals. Sodium is a basic radical while chloride is a acidic radical.
(e) Valency of carbon in CH₄ is 4, in C₂H₆ 4, in C₂H₄ 4 and in C₂H₂ is 4.
(f) Valency of Iron in FeCl₂ is 2 and in FeCl₃ it is 3.
(g) Formula of iron (III) carbonate is Fe₂(CO₃)₃.

2. Complete the following table.
Magnesium: MgCl₂, Mg(NO₃)₂, MgSO₄, MgCO₃, Mg(OH)₂, Mg₃(PO₄)₂
Sodium (Na⁺): NaCl, NaNO₃, Na₂SO₄, Na₂CO₃, NaOH, Na₃PO₄
Zinc (Zn²⁺): ZnCl₂, Zn(NO₃)₂, ZnSO₄, ZnCO₃, Zn(OH)₂, Zn₃(PO₄)₂
Silver (Ag⁺): AgCl, AgNO₃, Ag₂SO₄, Ag₂CO₃, AgOH, Ag₃PO₄
Ammonium (NH₄⁺): NH₄Cl, NH₄NO₃, (NH₄)₂SO₄, (NH₄)₂CO₃, NH₄OH, (NH₄)₃PO₄
Calcium (Ca²⁺): CaCl₂, Ca(NO₃)₂, CaSO₄, CaCO₃, Ca(OH)₂, Ca₃(PO₄)₂
Iron (II) (Fe²⁺): FeCl₂, Fe(NO₃)₂, FeSO₄, FeCO₃, Fe(OH)₂, Fe₃(PO₄)₂
Potassium (K⁺): KCl, KNO₃, K₂SO₄, K₂CO₃, KOH, K₃PO₄

3. Sodium chloride reacts with silver nitrate to produce silver chloride and sodium nitrate
(a) Write the equation.
(b) Check whether it is balanced, if not balance it.
(c) Find the weights of reactants and products.
(d) State the law which this equation satisfies.
(a) NaCl + AgNO₃ → AgCl + NaNO₃
(b) The equation is already balanced (1 Na, 1 Cl, 1 Ag, 1 N, 3 O on both sides).
(c) Atomic masses: Na=23, Cl=35.5, Ag=108, N=14, O=16.
Reactants weight:
NaCl = 23 + 35.5 = 58.5 g
AgNO₃ = 108 + 14 + (16×3) = 170 g
Total Reactants = 58.5 + 170 = 228.5 g
Products weight:
AgCl = 108 + 35.5 = 143.5 g
NaNO₃ = 23 + 14 + 48 = 85 g
Total Products = 143.5 + 85 = 228.5 g
(d) This satisfies the Law of Conservation of Mass (Matter is neither created nor destroyed).

4. What information does the following chemical equations convey?
(a) Zn + H₂SO₄ → ZnSO₄ + H₂
(b) Mg + 2HCl → MgCl₂ + H₂
(a) It conveys that:
- One atom of Zinc reacts with one molecule of Sulphuric acid.
- The products are one molecule of Zinc Sulphate and one molecule of Hydrogen gas.
- Zinc displaces hydrogen from the acid.
(b) It conveys that:
- One atom of Magnesium reacts with two molecules of Hydrochloric acid.
- The products are one molecule of Magnesium Chloride and one molecule of Hydrogen gas.
- Quantitative ratio: 24 parts by weight of Mg react with 73 parts by weight of HCl.

5. (a) What are poly-atomic ions? Give two examples.
(b) Name the fundamental law that is involved in every equation.
(a) Poly-atomic ions (or compound radicals) are ions composed of two or more different atoms acting as a single unit with a net charge.
Examples: Sulphate (SO₄^2-), Ammonium (NH₄⁺).
(b) The Law of Conservation of Mass.

6. What is the valency of:
(a) fluorine in CaF₂
(b) sulphur in SF₆
(c) phosphorus in PH₃
(d) carbon in CH₄
(e) nitrogen in the following compounds: (i) N₂O₃ (ii) N₂O₅ (iii) NO₂ (iv) NO
(a) 1 (Calcium is 2, so F must be 1 to balance CaF₂).
(b) 6 (Fluorine is 1, so S must be 6 to balance SF₆).
(c) 3 (Hydrogen is 1, so P must be 3 to balance PH₃).
(d) 4 (Hydrogen is 1, so C must be 4 to balance CH₄).
(e) Nitrogen valency:
(i) N₂O₃: 3 (From 2x = 3*2 => 2x=6 => x=3)
(ii) N₂O₅: 5 (From 2x = 5*2 => 2x=10 => x=5)
(iii) NO₂: 4 (From x = 2*2 => x=4)
(iv) NO: 2 (From x = 1*2 => x=2)

7. Why should an equation be balanced? Explain with the help of a simple equation.
An equation should be balanced to comply with the Law of Conservation of Mass, which states that matter is neither created nor destroyed during a chemical reaction. The total number of atoms of each element on the reactant side must equal the total number of atoms on the product side.
Example: H₂ + O₂ → H₂O (Unbalanced - O is not equal).
Balanced: 2H₂ + O₂ → 2H₂O (Here, 4 H atoms and 2 O atoms are on both sides).

8. Write the balanced chemical equations of the following reactions.
(a) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
(b) 2KHCO₃ + H₂SO₄ → K₂SO₄ + 2CO₂ + 2H₂O
(c) Fe + H₂SO₄ → FeSO₄ + H₂
(d) Cl₂ + SO₂ + 2H₂O → H₂SO₄ + 2HCl
(e) 2AgNO₃ → 2Ag + 2NO₂ + O₂ (Decomposition by heat)
(f) 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O
(g) 4NH₃ + 5O₂ → 4NO + 6H₂O
(h) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
(i) 2ZnS + 3O₂ → 2ZnO + 2SO₂
(j) Al₄C₃ + 12H₂O → 4Al(OH)₃ + 3CH₄
(k) 4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂
(l) 2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 5Cl₂ + 8H₂O
(m) Al₂(SO₄)₃ + 6NaOH → 2Al(OH)₃ + 3Na₂SO₄ (If excess NaOH: Al(OH)₃ + NaOH → NaAlO₂ + 2H₂O. The prompt asks for sodium meta aluminate).
Full reaction for (m) producing meta aluminate: Al₂(SO₄)₃ + 8NaOH → 2NaAlO₂ + 3Na₂SO₄ + 4H₂O
(n) 2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂
(o) 2K₂Cr₂O₇ + 8H₂SO₄ → 2K₂SO₄ + 2Cr₂(SO₄)₃ + 8H₂O + 3O₂
(p) K₂Cr₂O₇ + 14HCl → 2KCl + 2CrCl₃ + 7H₂O + 3Cl₂
(q) S + 6HNO₃ → H₂SO₄ + 6NO₂ + 2H₂O
(r) 2NaCl + MnO₂ + 2H₂SO₄ → Na₂SO₄ + MnSO₄ + 2H₂O + Cl₂ (or NaHSO₄ depending on temp. The prompt says Sodium Hydrogen Sulphate).
Balanced for NaHSO₄: NaCl + MnO₂ + 2H₂SO₄ → NaHSO₄ + MnSO₄ + 2H₂O + Cl₂ (Wait, stoichiometry: 2NaCl + MnO₂ + 3H₂SO₄ -> 2NaHSO₄ + MnSO₄ + 2H₂O + Cl₂. Let's check: Cl: 2->2, Na: 2->2, Mn: 1->1, S: 3->3, H: 6 -> 2+4=6, O: 2+12=14 -> 8+4+2=14). Correct.

9. (a) Define atomic mass unit.
(b) Calculate the molecular mass of the following:
(i) CuSO₄.5H₂O
(ii) (NH₄)₂CO₃
(iii) (NH₂)₂CO
(iv) Mg₃N₂
Given atomic mass of Cu = 63.5, H = 1, O = 16, C = 12, N = 14, Mg = 24, S = 32
(a) Atomic mass unit (amu) is defined as exactly 1/12th the mass of one atom of carbon-12 isotope.
(b) Calculations:
(i) CuSO₄.5H₂O = 63.5 + 32 + (4×16) + 5(2×1 + 16)
= 63.5 + 32 + 64 + 5(18)
= 159.5 + 90 = 249.5
(ii) (NH₄)₂CO₃ = 2(14 + 4×1) + 12 + 3×16
= 2(18) + 12 + 48
= 36 + 60 = 96
(iii) (NH₂)₂CO (Urea) = 2(14 + 2×1) + 12 + 16
= 2(16) + 28
= 32 + 28 = 60
(iv) Mg₃N₂ = 3(24) + 2(14)
= 72 + 28 = 100

10. Choose the correct answer from the options given below.
(a) Modern atomic symbols are based on the method proposed by
(i) Bohr (ii) Dalton (iii) Berzelius (iv) Alchemist
(b) The number of carbon atoms in a hydrogen carbonate radical is
(i) one (ii) two (iii) three (iv) four
(c) The formula of iron (III) sulphate is
(i) Fe₃SO₄ (ii) Fe(SO₄)₃ (iii) Fe₂(SO₄)₃ (iv) FeSO₄
(d) In water, the hydrogen-to-oxygen mass ratio is
(i) 1:8 (ii) 1:16 (iii) 1:32 (iv) 1:64
(e) The formula of sodium carbonate is Na₂CO₃ and that of calcium hydrogen carbonate is
(i) CaHCO₃ (ii) Ca(HCO₃)₂ (iii) Ca₂HCO₃ (iv) Ca(HCO₃)₃
(a) (iii) Berzelius
(b) (i) one (Formula is HCO₃^-)
(c) (iii) Fe₂(SO₄)₃
(d) (i) 1:8 (Mass of 2H = 2, Mass of O = 16. Ratio 2:16 = 1:8)
(e) (ii) Ca(HCO₃)₂ (Ca is +2, HCO₃ is -1)

11. Correct the following statements
(a) A molecular formula represents an element.
(b) Molecular formula of water (H₂O) represents 9 parts by mass of water.
(c) A balanced equation obeys the law of conservation of mass and so does an unbalanced equation.
(d) A molecule of an element is always monoatomic.
(e) CO and Co both represent cobalt.
(a) A molecular formula represents a molecule of an element or a compound.
(b) Molecular formula of water (H₂O) represents 18 parts by mass of water (2 + 16 = 18).
(c) Only a balanced equation obeys the law of conservation of mass; an unbalanced equation does not.
(d) A molecule of an element can be monoatomic, diatomic, or polyatomic (e.g., O₂, P₄).
(e) Co represents Cobalt, while CO represents Carbon Monoxide.

12. Calculate the relative molecular masses of:
(a) CHCl₃
(b) (NH₄)₂Cr₂O₇
(c) CuSO₄.5H₂O
(d) (NH₄)₂SO₄
(e) CH₃COONa
(f) Potassium chlorate
(g) Ammonium chloroplatinate (NH₄)₂PtCl₆
(Note: Use standard atomic masses: C=12, H=1, Cl=35.5, N=14, Cr=52, Cu=63.5, S=32, Na=23, K=39, Pt=195)
(a) CHCl₃ = 12 + 1 + 3(35.5) = 13 + 106.5 = 119.5
(b) (NH₄)₂Cr₂O₇ = 2(14+4) + 2(52) + 7(16) = 36 + 104 + 112 = 252
(c) CuSO₄.5H₂O = 63.5 + 32 + 64 + 5(18) = 159.5 + 90 = 249.5
(d) (NH₄)₂SO₄ = 2(18) + 32 + 64 = 36 + 96 = 132
(e) CH₃COONa = 12 + 3(1) + 12 + 16 + 16 + 23 = 15 + 12 + 32 + 23 = 82
(f) KClO₃ = 39 + 35.5 + 3(16) = 74.5 + 48 = 122.5
(g) (NH₄)₂PtCl₆ = 2(18) + 195 + 6(35.5) = 36 + 195 + 213 = 444

13. Give the empirical formula of:
(a) Benzene (C₆H₆)
(b) Glucose (C₆H₁₂O₆)
(c) Acetylene (C₂H₂)
(d) Acetic acid (CH₃COOH) = C₂H₄O₂
(a) Ratio 6:6 = 1:1. Empirical Formula: CH
(b) Ratio 6:12:6 = 1:2:1. Empirical Formula: CH₂O
(c) Ratio 2:2 = 1:1. Empirical Formula: CH
(d) Ratio 2:4:2 = 1:2:1. Empirical Formula: CH₂O

14. Find the percentage mass of water in the Epsom salt MgSO₄.7H₂O.
Molecular Mass of MgSO₄.7H₂O:
Mg(24) + S(32) + 4O(64) + 7(H₂O)(18)
= 24 + 32 + 64 + 126 = 246
Mass of Water (7H₂O) = 7 × 18 = 126
Percentage of water = (126 / 246) × 100 = 51.22%

15. Calculate the percentage of phosphorus in:
(a) Calcium hydrogen phosphate Ca(H₂PO₄)₂
(b) Calcium phosphate Ca₃(PO₄)₂
(a) Ca(H₂PO₄)₂:
Mass = 40 + 2[2(1) + 31 + 4(16)] = 40 + 2[2 + 31 + 64] = 40 + 2[97] = 40 + 194 = 234
Mass of P = 2 × 31 = 62
% P = (62 / 234) × 100 = 26.5%
(b) Ca₃(PO₄)₂:
Mass = 3(40) + 2[31 + 64] = 120 + 2(95) = 120 + 190 = 310
Mass of P = 2 × 31 = 62
% P = (62 / 310) × 100 = 20%

16. Calculate the percentage composition of each element in Potassium chlorate, KClO₃.
Molecular Mass of KClO₃ = 39 (K) + 35.5 (Cl) + 3×16 (O)
= 39 + 35.5 + 48 = 122.5
% K = (39 / 122.5) × 100 = 31.83%
% Cl = (35.5 / 122.5) × 100 = 28.98%
% O = (48 / 122.5) × 100 = 39.18%

17. Urea is a very important nitrogenous fertilizer. Its formula is CON₂H₄. Calculate the percentage of carbon in urea.
Molecular Mass of Urea (CON₂H₄) = 12 (C) + 16 (O) + 2×14 (N) + 4×1 (H)
= 12 + 16 + 28 + 4 = 60
Mass of Carbon = 12
% Carbon = (12 / 60) × 100 = 20%

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Quick Review Flashcards - Click to flip and test your knowledge!

Question

What is the definition of an element according to the text?

Answer

An element is a simple and pure form of matter which cannot be decomposed into simpler substances.

Question

What is the smallest particle of an element that represents all its properties?

Answer

An atom.

Question

Molecules containing only one atom in their structure are classified as _____.

Answer

Monoatomic molecules.

Question

Provide an example of a diatomic molecule mentioned in the text.

Answer

Hydrogen ($H_{2}$).

Question

Which element is given as an example of a tetratomic molecule?

Answer

Phosphorus ($P_{4}$).

Question

Which element is given as an example of an octatomic molecule?

Answer

Sulphur ($S_{8}$).

Question

Who suggested using the initial letter of an element's name in capitals as its symbol?

Answer

Johann Berzelius.

Question

What is the Latin name for the element Gold?

Answer

Aurum.

Question

What is the Latin name for the element Silver?

Answer

Argentum.

Question

What is the Latin name for the element Mercury?

Answer

Hydrargyrum.

Question

What is the Latin name for the element Copper?

Answer

Cuprum.

Question

What is the Latin name for the element Lead?

Answer

Plumbum.

Question

What is the Latin name for the element Iron?

Answer

Ferrum.

Question

What is the Latin name for the element Sodium?

Answer

Natrium.

Question

What is the Latin name for the element Potassium?

Answer

Kalium.

Question

What is the Latin name for the element Tin?

Answer

Stannum.

Question

What is the Latin name for the element Antimony?

Answer

Stibium.

Question

What is the Latin name for the element Tungsten?

Answer

Wolfram.

Question

How is the second letter written in a chemical symbol consisting of two letters?

Answer

In small (lowercase).

Question

What does the symbol $Co$ represent in chemistry?

Answer

The element Cobalt.

Question

What does the formula $CO$ represent in chemistry?

Answer

The compound carbon monoxide.

Question

Besides the name of an element, what quantitative quantity does a symbol represent?

Answer

One atom of the element.

Question

The symbolic representation of a molecule is known as its _____.

Answer

Formula (or molecular formula).

Question

What does the subscript in a chemical formula such as $H_{2}O$ represent?

Answer

The number of atoms of that specific element in one molecule.

Question

Define valency in terms of combining capacity.

Answer

Valency is the combining capacity of an atom of an element or of a radical.

Question

Which element is used as the standard for measuring valency with a value of one (1)?

Answer

Hydrogen.

Question

According to the modern definition, what determines the valency of an atom?

Answer

The number of electrons that an atom can lose, gain, or share during a chemical reaction.

Question

Atoms that lose electrons to attain stability form positive ions known as _____.

Answer

Cations.

Question

Atoms that gain electrons to attain stability form negative ions known as _____.

Answer

Anions.

Question

Elements with one, two, or three electrons in their outermost shell are usually classified as _____.

Answer

Metals.

Question

Elements with five, six, or seven electrons in their outermost shell are usually classified as _____.

Answer

Non-metals.

Question

What term describes the phenomenon where an element exhibits more than one valency?

Answer

Variable valency.

Question

In naming compounds of elements with variable valency, which suffix is used for the lower valency?

Answer

The suffix "-ous".

Question

In naming compounds of elements with variable valency, which suffix is used for the higher valency?

Answer

The suffix "-ic".

Question

State the two common valencies of Iron ($Fe$).

Answer

2 and 3.

Question

What is the trivial name for the $Fe^{2+}$ ion?

Answer

Ferrous.

Question

What is the trivial name for the $Fe^{3+}$ ion?

Answer

Ferric.

Question

What is the modern IUPAC name for Stannous chloride ($SnCl_{2}$)?

Answer

Tin (II) chloride.

Question

What is a radical in chemistry?

Answer

An atom or a group of atoms of the same or different elements that behaves as a single unit with a positive or negative charge.

Question

What is the difference between a simple radical and a compound radical?

Answer

A simple radical is a single charged atom, whereas a compound radical is a group of two or more different atoms.

Question

Electropositive radicals are also known as _____ radicals.

Answer

Basic.

Question

Electronegative radicals are also known as _____ radicals.

Answer

Acid.

Question

What is the symbol and charge for the Ammonium radical?

Answer

$NH_{4}^{+}$.

Question

What is the symbol and charge for the Bicarbonate radical?

Answer

$HCO_{3}^{-}$.

Question

What is the symbol and charge for the Sulphate radical?

Answer

$SO_{4}^{2-}$.

Question

What is the symbol and charge for the Phosphate radical?

Answer

$PO_{4}^{3-}$.

Question

What is the symbol and charge for the Hydroxide radical?

Answer

$OH^{-}$.

Question

What is the name of the method used to write chemical formulae by interchanging valencies?

Answer

The criss-cross method.

Question

When naming a compound of a metal and a non-metal, which element is written first?

Answer

The metal.

Question

Which suffix is added to the non-metal in a binary compound of a metal and a non-metal?

Answer

The suffix "-ide".

Question

For the compound $NaClO$, what is the specific prefix used due to the low number of oxygen atoms?

Answer

The prefix "hypo-" (Sodium hypochlorite).

Question

How are the names of binary acids, such as $HCl$, generally formed?

Answer

By adding the prefix "hydro-" and the suffix "-ic" to the name of the second element.

Question

A symbolic representation of a chemical reaction using symbols and formulae is called a _____.

Answer

Chemical equation.

Question

In a chemical equation, substances that take part in the reaction are called _____.

Answer

Reactants.

Question

In a chemical equation, substances formed as a result of the reaction are called _____.

Answer

Products.

Question

What is a 'skeleton equation'?

Answer

An equation that represents a chemical change but is unbalanced.

Question

Why must a chemical equation be balanced?

Answer

To comply with the Law of Conservation of Matter, which states that matter is neither created nor destroyed.

Question

The standard method for balancing simple chemical equations described in the text is the _____ method.

Answer

Hit and trial.

Question

Identify one limitation of a chemical equation regarding the physical state of substances.

Answer

A standard equation does not tell us the physical state (solid, liquid, or gas) unless specified with letters like ($s$), ($l$), or ($g$).

Question

How is a catalyst represented in a chemical equation?

Answer

It is written above or below the arrow ($\\rightarrow$) separating reactants and products.