Chemical Formulae And Equation Module

PEMBIMBING RAKAN SEBAYA KIMIA 2008 TARIKH TEMPAT

: :

1 APRIL 2008 (SELASA) SEK MEN TEKNIK KEMAMAN

NAMA

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KELAS

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ANJURAN: PANITIA KIMIA SMaTKem

MODUL 1 CHEMICAL FORMULAE AND EQUATIONS

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Chemical Formulae 1. Write the symbol for the element. No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16 17 18 19 20

ELEMENT Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Vanadium Chromium Manganese Iron Cobalt Bromine Iodine Platinum Aurum Lead

SYMBOL

No. 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

ELEMENT Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Nickel Cuprum Zink Silver Tin Barium Rubidium Krypton Xenon Mercury

SYMBOL

2. Write the ionic formulae of the ions. NO 1. 2.

ION Lithium ion Sodium ion

FORMULA

NO 17 18 3

ION Oxide ion Bromide ion

FORMULA

3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Magnesium ion Potassium ion Calcium ion Aluminum ion Iron (III) ion Zinc ion Copper (II) ion Ammonium ion Iron (II) ion Tin ion Lead(II) ion Barium ion Hydrogen ion Silver ion

19 20 21 22 23 24 25 26

Chloride ion Iodide ion Hydroxide ion Sulphate ion Fluoride ion Nitrate ion Carbonate ion Phosphate ion

3. Write the chemical formulae of the substances below: NO

SUBSTANCE

CHEMICAL

NO

SUBSTANCE

FORMULA 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Calcium carbonate Magnesium nitrate Copper(II) sulphate Zink chloride Sodium hydroxide Magnesium oxide Magnesium chloride Barium hydroxide Barium sulphate Copper(II) 4

CHEMICAL FORMULA

17 18 19 20 21 22 23

Silver nitrate Potassium nitrate Sodium carbonate Sodium sulphate Lead(II) iodide Lead(II) nitrate Potassium nitrate

24 25 26

Potassium hydroxide Calcium chloride Copper (II) sulphate

11. 12. 13. 14. 15. 16.

carbonate Iron(II) oxide Iron(III) oxide Zink nitrate Ammonium chloride Ammonium sulphate Potassium sulphate

27 28 29 30

Hydrochloric acid Sulphuric acid Nitric acid Calcium carbonate

31

Carbon dioxide

32

Ammonia

WRITING CHEMICAL EQUATIONS  A chemical equation must be balanced  Make sure there always be the same number of atoms of each element on both side of the equation REACTANTS → PRODUCTS Example 1. Magnesium reacts with dilute hydrochloric acid to produce magnesium chloride and hydrogen gas. Write an equation to represent the reaction. Step 1 :

Write the correct chemical formula for each reactant and product Mg + HCl → MgCl2 + H2

Step 2 :

Balance the equation. Adjust the coefficients in front of the chemical formulae and not the subscripts in the formulae. Mg + 2HCl → MgCl2 + H2

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2. Sulphuric acid reacts with copper (II) oxide powder to produce copper (II) sulphate and water.

3. Calcium carbonate decomposed to produce calcium oxide and carbon dioxide gas.

Chemical Equation 1. Write chemical equation that represent the reaction below : (a)

Zinc + sulphuric acid

zinc sulphate

+

hydrogen

………………………………………………………………………………………… (b)

Copper(II) carbonate + hydrochloric acid

copper(II) chloride + water + carbon dioxide

……………………………………………………………………………………….. (c )

Lead(II) nitrate + Potassium iodide

lead(II) iodide + potassium nitrate

………………………………………………………………………………………. (d)

Potassium hydroxide

+ sulfuric acid

potassium sulphate + water

………………………………………………………………………………………. (e)

Magnesium + copper(II) sulphate

copper

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+

magnesium sulphate

……………………………………………………………………………………… (f) Burning of magnesium in air …………………………………………………………………………………….. (g) Magnesium react with sulfuric acid …………………………………………………………………………………….. (h) Sodium react with oxygen ……………………………………………………………………………………. (i) Sodium carbonate react with hydrochloric acid …………………………………………………………………………………… (j) Reaction between hydrochloric acid and sodium hydroxide ………………………………………………………………………………………

MODUL 2

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SOLVING NUMERICAL PROBLEMS INVOLVING CHEMICAL EQUATION

Things to remember !!! (A)

IONIC FORMULAE

Cations (+)

Anions (-) Mass ( g ) Molarmass

(B)

No. of moles =

(C)

No. of particles = No. of moles x NA

(D)

Volume of gas = No. of moles x Molar volume 8

(E)

No. of moles =

MV 1000

Notes (i) Molar mass = relative atomic mass or relative molecular mass of the substance (ii) NA = Avogadro constant, 6.02 x 1023 (iii)

Molar volume = 22.4 dm3 at STP or 24 dm3 at room conditions

NUMERICAL PROBLEMS INVOLVING CHEMICAL EQUATIONS Step 1 : Write a balanced chemical equation Step 2 : Identify substances involved in the calculation, A and B Step 3 : Convert the given information (mass/volume of gas/number of particles) of A into the number of moles Step 4 : Compare the mole ratio of A and B from the chemical equation Step 5 : Calculate the number of moles of B based on the mole ratio in the equation Step 6 : Convert the number of moles of B to the unit required in the question EXAMPLE 1 Calculate the mass of zinc required to react with excess hydrochloric acid to produce 6 dm3 of hydrogen gas at room conditions. [RAM: Zn,65; Cl,35.5; Molar volume: 24 dm3mol-1 at room conditions] Step 1 :

Zn + 2HCl → ZnCl2 + H2

Step 2 :

mass?

Step 3 :

No. of moles of H2

6 dm3 = 6 dm3 24 dm3

= 0.25 mol ≡ 1 mol of Zn

Step 4 :

1 mol of H2

Step 5 :

0.25 mol of H ≡ 0.25 mol of Zn 9

Step 6 :

Mass of Zn

= 0.25 x 65 = 16.25 g

EXAMPLE 2 0.46 g of sodium burns completely in chlorine gas at room conditions. Find the volume of chlorine gas. [RAM: Na, 23; Molar volume: 24 dm3 mol-1 at room conditions] Step 1 :

2Na + Cl2 → 2NaCl

Step 2 :

0.46g

Step 3 :

No. of moles of Na = 0.46 23 = 0.02 mol

Step 4 :

2 mol of Na

Step 5 :

0.02 mol of Na ≡ 0.01 mol of Cl2

volume?

≡ 1 mol of Cl2

Step 6 : Volume of Cl2 = 0.01 x 24 = 0.24 dm3 EXERCISES 1. CuCO3 → CuO + CO2 Copper (II) carbonate is decomposed when heated strongly as shown in the equation above. Find the mass of copper (II) oxide formed when 12.4 g of copper (II) carbonate is heated completely. [RAM: Cu,64; O,16; C,12]

2. 720 cm3 of propane gas burns in excess oxygen at STP. Find the mass of carbon dioxide formed. [RAM: C,12; H,1; O,16]

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3. Excess calcium carbonate reacts with 25 cm3 of 0.15 mol dm-3 hydrochloric acid. Calculate the volume of carbon dioxide gas released at room conditions. [Molar volume: 24 mol dm-3 at room conditions]

4. (i) (ii)

H2O2 → H2O + O2 Balance the equation above. Find the number of moles of H2O2 that decomposes if 11.2 dm3 oxygen gas is collected at STP. [RAM: H,1; O, 16; Molar volume : 22.4 dm3 mol-1 at STP]

5. The following equation is not balanced. Na2SO4 + BaCl2 → BaSO4 + NaCl (a) Identify the reactants and products of the reaction. (b) Balance the equation. Then, calculate (i)

the number of moles of sodium sulphate that react completely with a solution containing 2.08 g of barium chloride

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(ii)

the mass of barium sulphate formed when 1 mol of sodium sulphate is reacted with 1 mol of barium chloride

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