2(d) Reactivity series

order the metals in terms of reactivity

(anagram)

Please Send Lions, Cats, Monkeys, And Cute Zebras Into Hot Countries, Signed Gordon

Potassium

Sodium

Lithium

Calcium

Magnesium

Aluminium

Carbon

Zinc

(chromium)

Iron

(nickel, tin, lead)

Hydrogen

Copper

(mercury)

Silver

Gold

(platinum)

when metals react with water, what products do they form?

metal + water → metal hydroxide + hydrogen

what happens when potassium, sodium, lithium, and calcium react with water?

potassium: reacts violently

sodium: reacts quickly

lithium: reacts less strongly

calcium: reacts less strongly

what are the equations for potassium, sodium, and lithium reacting in water?

2 K_(s) + 2 H₂O_(l) → 2 KOH_(aq) + H_{2 (l)}

2 Na_(s) + 2 H₂O_(l) → 2 NaOH_(aq) + H_{2 (l)}

2 Li_(s) + 2 H₂O_(l) → 2 LiOH_(aq) + H_{2 (l)}

what is the equation for calcium reacting in water?

Ca_(s) + 2 H₂O_(l) → Ca(OH)_{2 (aq)} + H_{2 (g)}

what happens when iron, magnesium, and zinc react with water?

very slow reactions

iron rusts slowly

what common dilute acids can be reacted with metals?

sulfuric acid

hydrochloric acid

when a metal reacts with an acid, what products are formed?

metal + acid → salt + hydrogen

where does a metal have to be in the reactivity series to be able to react with a dilute acid?

above hydrogen

which common metals are used to react with dilute acids?

magnesium

zinc

iron

what are the equations for when magnesium, zinc, and iron react with dilute sulfuric acid?

Mg_(s) + H₂SO_{4 (aq)} → MgSO_{4 (aq)} + H_{2 (g)}

Zn_(s) + H₂SO_{4 (aq)} → ZnSO_{4 (aq)} + H_{2 (g)}

Fe_(s) + H₂SO_{4 (aq)} → FeSO_{4 (aq)} + H_{2 (g)}

TIP: the metal ions have a charge of 2+, and SO₄ has a charge of 2-, which makes it easy to remember why they are used

what are the equations for when magnesium, zinc, and iron react with dilute hydrochloric acid?

Mg_(s) + 2HCl_(aq) → MgCl_{2 (aq)} + H_{2 (g)}

Zn_(s) + 2HCl_(aq) → ZnCl_{2 (aq)} + H_{2 (g)}

Fe_(s) + 2HCl_(aq) → FeCl_{2 (aq)} + H_{2 (g)}

TIP: the metals ions have a charge of 2+, and Cl has a charge of 1-, which makes 2 the magic number for the acid

what is a metal displacement reaction?

when a more reactive metal displaces a less reactive metal in a compound

what are 2 examples of metal displacement reactions?

reacting a metal with a metal oxide by heating

reacting a metal with an aqueous solution of a metal compound

describe the reaction of magnesium and copper (II) sulfate (2 details)

the blue colour of the solution fades as colourless magnesium sulfate forms

copper coats the surface of the magnesium and forms a solid metal, which falls to the bottom of the beaker

what are the conditions needed for iron to rust?

water + oxygen

describe an experiment to investigate the conditions for rusting

3 test tubes with iron nails in them

the first has air and water

the second has water but no air (boiled water with a layer of oil on top)

the third has air but no water (calcium chloride to remove water)

the first rusts, the other two do not

what are the three methods of preventing rust?

barrier methods

sacrificial protection

galvanising

how do barrier methods prevent iron from rusting?

what are some examples of barrier methods? (4)

what cons are there to this method?

prevent iron from coming into contact with water and oxygen

paint, oil, grease, electroplating

if coatings are washed away/scratched, the iron is exposed

because rust is porous, if iron starts to rust, it also starts to corrode internally

how does sacrificial protection prevent iron from rusting?

where is this type of rust prevention used?

what cons are there to this method?

a more reactive metal (commonly zinc) is attached to a body of iron

the more reactive metal oxidises and corrodes before the iron

ship hulls

the zinc bars have to be replaced before they corrode fully

how does galvanisation prevent iron from rusting?

what type of method is this?

what pros are there to this method?

iron is coated with a layer of zinc, either by electroplating or dipping the object into molten zinc

ZnCO₃ is formed when the zinc reacts with oxygen and CO₂ in the atmosphere

the ZnCO₃ protects the iron

barrier method

if the coating is scratched, the iron is still protected due to sacrificial protection

define oxidation and reduction (not in terms of electrons)

oxidation: when a substance gains oxygen

reduction: when a substance loses oxygen

what type of reaction is one where oxidation and reduction occurs?

a redox reaction

what is the equation for the reaction between zinc and copper oxide? (Zn + CuO)

Zn + CuO → ZnO + Cu

Zn + CuO → ZnO + Cu

what is the oxidising agent in this reaction?

what is the reducing agent in this reaction?

Cu is the oxidising agent, because it supplies oxygen

Zn is the reducing agent, because it takes oxygen

what is the equation for magnesium + copper sulfate in terms of ions? (Mg + CuSO₄)

Mg_(s) + Cu²⁺_(aq) + SO₄^2-_(aq) → Mg²⁺_(aq) + SO₄^2-_(aq) + Cu_(s)

Mg_(s) + Cu²⁺_(aq) + SO₄^2-_(aq) → Mg²⁺_(aq) + SO₄^2-_(aq) + Cu_(s)

identify the spectator ions in this equation and turn it into an ionic equation

Mg_(s) + Cu²⁺_(aq) + SO₄^2-_(aq) → Mg²⁺_(aq) + SO₄^2-_(aq) + Cu_(s)

spectator ions appear unchanged on both sides of the equation

Mg_(s) + Cu²⁺_(aq) → Mg²⁺_(aq) + Cu_(s)

to form an ionic equation, remove the spectator ions

Define oxidation and reduction in terms of electrons

oxidation is loss

reduction is gain

(OILRIG)

Mg_(s) + Cu²⁺_(aq) → Mg²⁺_(aq) + Cu_(s)

split this ionic equation into two half equations

which element is oxidised and which is reduced?

which element is the oxidising agent and which is the reducing agent?

Mg → Mg²⁺ + 2e^-

Cu²⁺ + 2e^- → Cu

Mg is the oxidised, and is the reducing agent

Cu²⁺ is the reduced, and is the oxidising agent

describe an experiment to investigate metals reacting with dilute acids

what should the results show?

Method:

1. wear safety goggles (acids)

2. add 5cm³ of dilute sulfuric acid to 3 test tubes

3. add a magnesium ribbon to the first, iron filings to the second, and zinc turnings to the third. try and keep their volumes similar

4. record your observations and test for any gases given off with a lit splint

5. repeat with dilute HCl

Results:

The results should show that, ranked in reactivity order: Mg > Zn > Fe