S3 Chemistry

Unit 2Formulae and

Reaction Quantities

Name ______________________1

Teacher ____________________

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Notes

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GlossaryValency The valency of an atom is the number of bonds it is able to

make with other atoms.Mole One mole of a substance contains 6.02 x 1023 particles

(similar to how a dozen means 12). This number is known as the Avogadro constant.

Gram Formula Mass

The Gram Formula Mass is the mass in grams of one mole of a substance

Formula Mass The total mass of all atoms in a formula, no units.Concentration The concentration of a solution is a measure of the number

of moles of the solute in 1 litre of the solvent.Conservation of Mass

No Mass is lost or gained in a reaction i.e. the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning

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Naming and Word EquationsRemember

1. What is the name given to the attractive forces which hold atoms together in molecules?

2. What is the name given when different elements are put together but do not react and join?

3. What is the name given when different elements are mixed and they do react and join?

4. What are the five signs of a chemical reaction?5. What is the difference between a chemical reaction and a physical

change?Naming Compounds

‘-ide’ rule: Compounds made from t_ _ elements always end in -ide‘-ate’ and ‘-ite’ rule: Compounds containing t_ _ _ _ elements, one of

which is always o_ _ _ _ _ end in -ate or -iteOne exception is -OH containing compoundsE.g. LiOH is called Lithium Hydroxide

Elements Present Compound NameSodium, Sulphur, Oxygen

Potassium nitrateCalcium, Carbon, Oxygen

Magnesium chloridePotassium, OxygenSodium, Hydrogen, Oxygen

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Word Equations

This is a representation of a c_ _ _ _ _ _ _ reaction.Magnesium reacts with oxygen to produce magnesium o_ _ _ _.Reactants: Products:What to remember:

1. We use not ‘=’

The arrow means ‘r_ _ _ _ _ to give’

Hydrogen gas is burned in oxygen and water is formed.

2. Reactants P_ _ _ _ _ _ _

Calcium carbonate reacts with hydrochloric acid producing calcium chloride, water and carbon dioxide

The e_ _ _ _ _ _ _ present in the reactants are also present in the products.

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1. Carbon monoxide burning to form carbon dioxide.

2. Methane burning to form water and carbon dioxide.

3. Hydrogen sulphide burning to form water and sulphur dioxide.

4. Sodium chloride being produced from sodium and chlorine.

5. When hot lithium is placed in bromine vapour the two elements react to produce lithium bromide.

6. When sodium is heated in a Bunsen flame it bursts into flames, combining with oxygen to form sodium oxide.

7. Hydrogen and chlorine combine explosively in bright light to produce hydrogen chloride.

8. Silicon hydride burns spontaneously in air to produce silicon dioxide and water.

9. Calcium reacts quickly with water to produce calcium hydroxide and hydrogen.

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Writing FormulaeValency

The v_ _ _ _ _ _ of an atom is the number of bonds it is able to make with other atoms.Method 1: Valency Pictures

Group 1 2 3 4 5 6 7 8/0Valenc

y

Magnesium Sulphide

Mg is in group _ S is in group _ Formula:Valency = Valency = Calcium chloride

Aluminium oxide

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Method 2: SVSDFSVSDF

Potassium oxide Aluminium oxideS SV VS SD DF F

Use your preferred method and determine the formulae of the following:

Aluminium hydride Carbon sulphide Magnesium oxide

Sodium chloride Carbon chloride Carbon fluoride

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Group Ion Formulae

Some ions contain more than one element.- the c_ _ _ _ _ _ _ _ ion contains carbon and oxygen. CO3

- the s_ _ _ _ _ _ _ _ ion contains sulphur and oxygen. SO4

The valency on Page 8 of the data book refers to the whole ion.

Examples:Lithium Carbonate Calcium nitrateS SV VS SD DF F

Use your preferred method and determine the formulae of the following:Lithium nitrate Calcium carbonate Calcium chromate

Barium sulphate Aluminium nitrate Magnesium nitrate

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Transition Metal Formulae

Roman Numeral

I II III IV V

Number

Some metals have more than one possible v_ _ _ _ _ _. This valency is given as a roman numeral in the name of the compound, e.g. Iron(_ _) chloride.

Example:Iron (II) chlorideSVSDF

Use your preferred method and determine the formulae of the following:Copper (II) chloride Silver (I) oxide Iron (III) oxide

Lead (II) fluoride Nickel (I) sulphide Gold (III) iodide

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Prefixes

Prefixes are used in compounds that b_ _ _ _the valency rules, such as carbon monoxide and sulphur trichloride.

Prefix Value

MonoDiTri

TetraPentaHexa

Determine the formulae of the following compounds:

Nitrogen monoxide Disilicon tetrachloride

Phosphorus pentachloride Sulphur trioxide

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Balancing Equations

Recap: Write the word equations for the following reactions:1. Burning carbon in excess oxygen to make carbon dioxide.

2. Magnesium reacting with chlorine gas to make magnesium chloride.

3. Iron reacting with oxygen to produce Iron (II) oxide

Conservation of Mass

A_ _ _ _are the smallest particles of an element that can take part in a chemical reaction. During any chemical reaction n_ p_ _ _ _ _ _ _ _ are created or destroyed: the atoms are simply r_ _ _ _ _ _ _ _ _ from the reactants to the products. The products may have different properties to the reactants.

Mass is n_ _ _ _ l_ _ _ or g_ _ _ _ _in chemical reactions. We say that mass is always c_ _ _ _ _ _ _ _. In other words, the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.

This fact allows you to work out the mass of one substance in a reaction if the masses of the other substances are known. 

Balancing Formula Equations

Three things are balanced in a chemical equation:1. 2. 3.

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Steps to balance an equation: Write out a formula equation Make a list of all atoms present on the Reactant and Products side

(these should have the same elements!) Put a number (coefficient) in front of the compound to multiply the

number of every atom present. Continue to do this until the number of each atom matches on the

reactant and product sides.

Example:Fe + O2 FeOFe FeO O

Balance the following equations:1. Mg + O2 MgO

2. Mg + AgNO3 Mg(NO3)2 + Ag

3. NaOH + H2SO4 Na2SO4 + H2O

4. Al + Cl2 AlCl3

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Gram Formula Mass (GFM)

Remember: Mass Number = RAM =

(RAM values found in Data Book Page 7)

Formula Mass

The total mass of all atoms in a formula is called the F_ _ _ _ _ _ M_ _ _.Examples:

Ne H2

Sulphur dioxide,

Gram Formula Mass (GFM)

The Gram Formula Mass of a substance is the Formula Mass written in g_ _ _ _.

Substance Formula Formula Mass GFMNeon Ne

HydrogenSulphur dioxide

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Work out the Formulae and GFM for the following:

Lithium oxide Magnesium hydroxide

Aluminium Carbonate Copper (II) oxide

Carbon dioxide

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The Mole

The Gram Formula Mass is the m_ _ _, in g_ _ _ _, of o_ _ mole of a substance.

Calculate the mass of 1 mole of the following substances:

Carbon, C Magnesium, Mg

Chlorine, Carbon monoxide,

Hydrogen oxide, Sodium oxide,

The Mole and Mass Triangle

n = m =

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Examples:

Calculate the mass of 2 moles of Sodium chloride (NaCl).

NaCl m = n x GFM

How many moles are there in 36g of water (H2O)?

H2O n = m / GFM

Calculate the number of moles for each of the following substances:

20 g of Calcium 54 g of Hydrogen oxide

12 g of Helium 14 g of Nitrogen gas

10 g of Calcium carbonateCaCO3

280 g of Carbon monoxide

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Calculate the mass of each of the following substances:

2 moles of Carbon 0.5 moles of Magnesium

3 moles of Hydrogen 2.5 moles of Carbon dioxide

1.5 moles of Copper (I) oxide 4 moles of Hydrogen chloride

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The Mole and Solutions

ConcentrationThe concentration of a solution is a measure of the number of m_ _ _ _ of the s_ _ _ _ _in 1 litre of the s_ _ _ _ _ _.

Concentrations can be expressed as the number of moles in a particular volume or the number of grams in a particular volume.• Units: ______ or ______

______ or ______

A concentrated solution will have a l_ _ _ _ number of particles of the solute in a given volume of solvent. A d_ _ _ _ _ solution will have a small number of particles of the solute in a given volume of solvent.

V_ _ _ _ _ must be in litres. If you have two of the variables in the triangles then you can work out the third.

n = C = V =

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Calculate the concentration of the following:1. 0.5 mole of sodium chloride in 500 cm3 of solution.

2. 2 mole of nitric acid in 4000 cm3 of solution.

Calculate the number of moles in the following:1. 200 cm3 of a 2 mol l -1 solution of potassium hydroxide.

2. 1800 cm3 of a 0.25 mol l -1 solution of cobalt(II) chloride.

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Concentration and Mass Calculations

Concentration to Mass Calculation

Given C and V calculate m. Requires 2 calculations.

1.

Then

2.

Example 1:Calculate the mass of sodium hydroxide (NaOH) present in 250 cm3 of a 1 moll-1 solution.

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Example 2:Calculate the mass of magnesium bromide (MgBr2) present in 2.5l of a 0.75moll-1 solution.

Mass to Concentration Calculation

Given m and V calculate C. Requires 2 calculations.

1.

Then2.

Example 3:A 500 cm3 solution contains 34.8 g of potassium sulphate (K2 SO4). Calculate the concentration of the solution.

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Example 4:A 2l solution contains 29.25 g of sodium chloride(NaCl). Calculate the concentration of the solution.

Answer the following:

1. A laboratory technician was asked to make up a solution of sodium carbonate. She weighed out 10.6g of sodium carbonate (Na2CO3), dissolved it in a little water then made the solution up to exactly 500 cm3.Calculate the concentration of the resulting solution.

2. Calculate the mass of Copper(II) sulphate required to prepare 250cm3 of a solution of concentration 0.15 mll-1.

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Exercise 1: Formulae

1. Hydrogen chloride 2. Barium Oxide

3. Hydrogen iodide 4. Phosphorus oxide

5. Potassium oxide 6. Hydrogen sulfide

7. Calcium sulphide 8. Nitrogen chloride

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Exercise 2: Group Ion Formulae

1. sodium hydroxide 2. ammonium carbonate

3. aluminium sulphate 4. sodium sulphate

5. ammonium iodide 6. calcium phosphate

7. aluminium hydroxide 8. sodium hydrogencarbonate

9. barium dichromate 10.potassium hydrogensulphite

11. lithium phosphate 12. ammonium carbonate

Exercise 3: Transition Metal Formulae

1. tin (IV) chloride 2. chromium (III) fluoride

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3. iron (III) chloride 4. copper (I) iodide

5. vanadium (V) oxide 6. cobalt (II) chloride

7. silver (I) sulphide 8. titanium (III) nitride

9. nickel (I) fluoride 10. copper (II) oxide

11. copper (I) sulphide 12. mercury (I) bromide

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Exercise 4: Balancing Equations

1. Fe + H2SO4 Fe2(SO4)3 + H2

2. CH4 + O2 CO2 + H2O

3. AgI + Na2S Ag2S + NaI

4. NH3 + O2 NO + H2O

5. NaBr + Cl2 NaCl + Br2

6. (NH4)3PO4 + Pb(NO3)4 Pb3(PO4)4 + NH4NO3

Exercise 5: Gram Formula Mass

Name Formula GFMLithium sulphide

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Sodium hydroxide

Potassium sulphate

Ammonium nitrate

Iron (III) oxide

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Exercise 6 – The Mole

Calculate the number of moles:

1. 10g of Hydrogen gas 2. 10.1g of potassium nitrate

3. 8g of sulphur 4. 6.6g of ammonium sulphate

5. 2 moles of iron 6. 1.5 moles of sodium oxide

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Calculate the mass of the following:

1. 456.25 g of nickel(II) nitrate 2. 6 g of water

3. 6.4g of oxygen 4. 693 g of ammonium sulphate

5. 33.3 g of calcium chloride 6. 40 g of bromine

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Exercise 7: The Mole and Solutions

Calculate the concentration of the following:

1. 0.25 mole of potassium carbonate in 200 cm3 of solution.

2. 1.5 mole of nickel(II) sulphate in 3 litres of solution.

3. 0.05 mole of lithium bromide in 50 cm3 of solution.

Calculate the number of moles in the following:

1. 75 cm3 of a 0.5 mol l -1 solution of phosphoric acid.

2. 2 litres of a 0.4 mol l -1 solution of zinc nitrate.

3. 750 cm3 of a 3 mol l -1 solution of copper(II) chloride.

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Exercise 8: Mass and Concentration Calculations

Calculate the mass of compound in the following solutions:1. 100 cm3 of a 0.5 mol l -1 solution of sulphuric acid (H2SO4).

2. 2 litres of a 0.4 mol l -1 solution of potassium nitrate (KNO3).

3. 250 cm3 of a 1.5 mol l -1 solution of tin(II) sulphate (SnSO4).

4. 2500 cm3 of a 0.2 mol l -1 solution of copper(II) chloride (CuCl2).

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Calculate the concentration of the following solutions:1. 5 g of sodium hydroxide [NaOH] in 500 cm3 of solution.

2. 273 g of zinc chloride [ZnCl2] in 1500 cm3 of solution.

3. 37.125 g of magnesium nitrate [Mg(NO3)2] in 400 cm3 of solution.

4. 59.6 g of ammonium phosphate [(NH4)3PO4] in 2 litres of solution.

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