chemical changes (required practical)

Question 1

is a high pH acid or alkaline?

Answer 1

alkaline.

Question 2

is a low pH acid or alkaline?

Answer 2

acid.

Question 3

how do you measure the pH of a solution?

Answer 3

an indicator. such as universal indicator
pH probe. attached to a pH meter

Question 4

what is an acid?

Answer 4

a substance that forms hydrogen ions when dissolved in water. also has a pH less than 7

Question 5

what is a base?

Answer 5

a substance with a pH higher than 7. and can neutralise acids

Question 6

what is an alkali?

Answer 6

a base that forms hydroxide ions when dissolved in water.

Question 7

what is a neutralisation?

Answer 7

the reaction between an acid and a base.
acid + base → salt + water

Question 8

what is the symbol equation for neutralisation using H and OH ions?

Answer 8

H+ + OH- → H₂O

Question 9

how do you find a concentration using titration? (practical) acid and alkali can be interchanged

Answer 9

1. add a set volume of an alkali with an unknown concentration to a conical flask. with a pipette
2. add a few drops of phenolphthalein.
3. use a funnel to fill a burette vertically clamped with an acid of known concentration. then remove the funnel
4. record the volume of acid in the burette.
5. add a small amount of acid to the alkali at a time stirring regularly.
6. when the phenolphthalein turns from pink to colourless stop adding.
7. record the final volume of acid in the burette to calculate the volume of acid needed to neutralise the alkali.
8. repeat the test multiple times for concordant results and an average volume.
   for an acid of unknown concentration switch acid and alkali and use methyl orange (red to yellow)

Question 10

what do acids produce in water?

Answer 10

hydrogen ions.

Question 11

what is a strong acid?

Answer 11

an acid that ionises completely in water. all acid particles disassociate

Question 12

what is a weak acid?

Answer 12

an acid that does not completely ionise in water. only some acid particles disassociate

Question 13

why are strong acids more reactive than weak acids?

Answer 13

strong acids have a higher H+ ion concentration. reactions of acids involve H+ ions reaction with other substances

Question 14

what is pH a measure of?

Answer 14

the concentration of H+ ions.

Question 15

what factor does H+ ion concentration increase by ever pH decrease?

Answer 15

x10.

Question 16

what is the difference between acid concentration and strength?

Answer 16

acid strength is how much of the acid molecules ionise in water.
acid concentration is how much acid there is in a certain volume of water. base on how watered down your acid is

Question 17

what do metal oxides and hydroxides react with acid to produce?

Answer 17

acid + metal oxide → salt + water
acid + metal hydroxide → salt + water

Question 18

what do metal carbonates react with acid to produce?

Answer 18

acid + metal carbonate → salt + water + carbon dioxide

Question 19

how do you make a soluble salt using an insoluble base? (practical)

Answer 19

1. pick the right acid and insoluble base.
2. warm the acid using a bunsen burner.
3. add the insoluble base to the acid a bit at a time until the base is in excess. after stirring there will be residue
4. filter the solution to remove excess.
5. heat the solution with a water bath to evaporate some of the water to increase the concentration then leave it to cool.
6. crystals should form over time which can be filtered out and dried.

Question 20

what is the reactivity series.

Answer 20

a list of metals in order of their reactivity to other substances.

Question 21

what determines a metal’s reactivity?

Answer 21

how easily it loses its electrons. to form positive ions

Question 22

what are the first 10 substances of the reactivity series? in order

Answer 22

1. potassium. K
2. sodium. Na
3. lithium. Li
4. calcium. Ca
5. magnesium. Mg
6. carbon. C
7. zinc. Zn
8. iron. Fe
9. hydrogen. H
10. copper. Cu

Question 23

what does acid and metal react to produce?

Answer 23

acid + metal → salt + hydrogen

Question 24

how can you measure the reactivity of a metal and acid? (2)

Answer 24

the rate that hydrogen bubbles are given off.
the temperature change of the reaction over a period of time.

Question 25

what does metal and water react to produce?

Answer 25

metal + water → metal hydroxide + hydrogen

Question 26

what are 4 metals that react with water?

Answer 26

1. potassium. 2. sodium. 3. lithium. 4. calcium.

Question 27

what is oxidisation?

Answer 27

when metal reacts with oxygen to form oxides.

Question 28

what is a reduction reaction?

Answer 28

a reaction that separates a metal form its oxide.

Question 29

what element is commonly used for reduction reactions?

Answer 29

carbon. *carbon gains oxygen removed from an ore*

Question 30

how does a metals place in the reactivity series determine if it can be extracted by reduction with carbon?

Answer 30

carbon can be used if the metal is lower than carbon in the reactivity series. *carbon is more reactive*

Question 31

if a metal is higher than carbon on the reactivity scale how can it be extracted?

Answer 31

with electrolysis.

Question 32

what is oxidation and reduction in terms of electrons and oxygen?

Answer 32

reduction loses oxygen and gains electrons. oxidation gains oxygen and loses electrons.

Question 33

what is a redox reaction?

Answer 33

reduction and oxidation happen at the same time called a redox. *also when electrons are transferred*

Question 34

what is a displacement?

Answer 34

a more reactive element kicking out a less reactive element.

Question 35

what will happen if you put a reactive metal in a solution of a dissolved metal compound?

Answer 35

the more reactive metal will replace the less reactive metal in the compound.

Question 36

what is an ionic equation?

Answer 36

an equation that only shows the particles that react and the products they form *it leaves out anything that stays the same*