C5 - Chemical changes

Question 1

Recall the reactivity series:

Answer 1

-potassium
-sodium
-lithium
-calcium
-magnesium
-aluminium
-CARBON
-zinc
-iron
-tin
-lead
-HYDROGEN
-copper
-silver
-gold

(Please Stop Laughing Cuz My Animals Can Zip Into The Large House Cuz Snakes Glow)

Question 2

What determines a metal’s reactivity?

Answer 2

its tendency to form a positive ion

Question 3

What defines a metal ore?

Answer 3

a metal ore contains enough metal to make it economically worthwhile to extract it

Question 4

When do metals need to be extracted? How are they extracted?

Answer 4

-if the metal is reactive enough, it will be found in the Earth as an oxide compound
-elements less reactive than carbon can be extracted using carbon in a reduction reaction (removes oxygen)

It won’t need to be extracted if it is unreactive, like gold

Question 5

What is oxidation and reduction in terms of electrons?

Answer 5

oxidation is loss of electrons

reduction is gain of electrons

(OIL, RIG)

Question 6

metal + water →

Answer 6

metal hydroxide + hydrogen

Question 7

metal + acid →

Answer 7

salt + hydrogen

Question 8

acid + metal hydroxide →

Answer 8

salt + water

Question 9

acid + metal oxide →

Answer 9

salt + water

Question 10

acid + metal carbonate →

Answer 10

salt + water + carbon dioxide

Question 11

What is the difference between an alkali and a base?

Answer 11

-alkalis dissolve in water to form a solution of pH > 7

-bases are insoluble in water

Question 12

Give some examples of insoluble bases:

Answer 12

-metal oxides
-metal carbonates
-metal hydroxides (mostly)

Lithium, sodium, and potassium hydroxides are soluble, but all others are not

Question 13

RP1 - How can you prepare a dry sample of a soluble salt using an acid and an insoluble solid?

Answer 13

-pour acid in beaker and heat gently over a BB (^RoR)
-add insoluble solid until no more reacts
-filter off excess solid with funnel + filter paper
-evaporate solution until crystals begin to form using a boiling water bath
-leave solution to finish crystallising for a few days, and gently pat crystals dry with filter paper

Question 14

Why are acids acidic and alkalis alkaline? How can you measure their pH?

Answer 14

-acids produce H+ ions in water, and alkalis produce OH- ions

-measure with UI or pH probe

Question 15

How does the colour of UI change when in solutions of different pH?

Answer 15

same as light spectrum - ROYGBIV

Question 16

How can a general neutralisation reaction be represented?

Answer 16

Question 17

What is the difference between a strong and weak acid? Give some examples of each:

Answer 17

-strong acids are completely ionised in aqueous solution (hydrochloric, nitric, sulfuric)

-weak acids are partially ionised in aqueous solution (ethanoic, citric, carbonic, phosphoric)

Question 18

Why can an acid be described as both strong and dilute?

Answer 18

-strong because completely ionised in aqueous solution
-dilute because small amount of acid per unit volume

Question 19

How does the hydrogen ion concentration change with pH?

Answer 19

as pH decreases by one unit, H+ ion concentration increases by a factor of 10 (logarithmic)

Question 20

Copper, copper carbonate, and copper oxide are all mixed with hydrochloric acid - which of the compounds react to form a salt?

Answer 20

-only copper carbonate and copper oxide

-copper itself is below hydrogen in the reactivity series, and can’t displace it