C6 - Making Useful Chemicals

Question 1

what is an acid?

Answer 1

a substance with a pH less than 7

Question 2

what is an alkali?

Answer 2

a solution that has a greater pH than 7

Question 3

true or false: the higher the hydrogen ion concentration, the more acidic something is

Answer 3

true

Question 4

what ways can you measure the pH?

Answer 4

an indicator
a pH probe attached to a pH meter

Question 5

what happens if the H+ ions increases by 10?

Answer 5

the pH decreases by 1, becoming more acidic

Question 6

what happens to acids when they ionise?

Answer 6

they produce hydrogen ions, H+

Question 7

what type of acid completely ionises in water?

Answer 7

strong acids
all acid molecules dissociate to release H+ ions

Question 8

what type of acid does not fully ionise in solution?

Answer 8

weak acids
only a small proportion of acid molecules dissociate to release H+ ions

Question 9

why do strong acids react quicker than weaker acids?

Answer 9

because the concentration of H+ ions is higher

Question 10

what is formed during a neutralisation reaction?

Answer 10

a salt is formed

Question 11

acid + metal hydroxide →

Answer 11

acid + metal hydroxide → salt + water

Question 12

acid + metal →

Answer 12

acid + metal → salt + hydrogen

Question 13

acid + metal carbonate →

Answer 13

acid + metal carbonate → salt + water + carbon dioxide

Question 14

what is the rate of reaction?

Answer 14

how quickly the reaction happens

Question 15

reaction rates can be explained using collision theory. this states the rate of reaction depends on:

Answer 15

1. the collision frequency of reacting particles
2. the energy transferred during a collision

Question 16

why do higher temperatures increase the rate of reaction?

Answer 16

increases energy of collisions
since particles are moving faster
at higher temps there will be more frequent, successful collisions

Question 17

why does increasing concentration increase the rate of reaction?

Answer 17

more particles of reactant in the same volume, which makes collisions more likely

Question 18

why does smaller solid particles increase the rate of reaction?

Answer 18

the particles around it will have more area to work on, so the frequency of collisions will increase

Question 19

why does a catalyst increase the rate of reaction?

Answer 19

as catalysts work by decreasing the activation energy needed for the reaction to occur, by providing an alternative reaction pathway with lower activation energy

Question 20

what is a catalyst?

Answer 20

is a substance that speeds up the rate of reaction without being used up by itself

Question 21

what are enzymes?

Answer 21

are proteins that act as biological catalysts
catalyse chemical reactions in cells
work best in specific conditions

Question 22

what is the calculation for the rate of reaction?

Answer 22

amount of reactant used or amount of product formed / time

Question 23

what are the 3 ways you can measure the rate of reaction?

Answer 23

1. precipitation and colour change
2. change in mass (gas)
3. the volume of gas has given off

Question 24

how do you calculate the mean reaction rate from a graph?

Question 25

how do you find the reaction rate at a particular point?

Answer 25

draw the tangent at the point where you want to know the rate

Question 26

what is a reversible reaction?

Answer 26

is one where the products can react with each other to produce the original reactants

Question 27

what is the dynamic equilibrium?

Answer 27

both reactions are still happening but there is no overall effect this means that the concentrations of reactants and products have reached a balance and won't change

Question 28

what is a closed system?

Answer 28

just means that none of the reactants or products can escape and nothing

Question 29

what are the three things that can change the position of the equlibirum?

Answer 29

temperature pressure (gases only) concentration

Question 30

what happens if you decrease the temperature in an equilibrium?

Answer 30

the equilibrium will move in the exothermic direction to produce more heat

Question 31

what happens if you increase the temperature in an equilibrium?

Answer 31

the equilibrium will move in the endothermic direction to absorb the extra heat

Question 32

what happens if you increase the pressure in an equilibrium?

Answer 32

the equilibrium will move towards the side that has fewer moles of gas to reduce pressure

Question 33

what happens if you decrease the pressure in an equilibrium?

Answer 33

the equilibrium will move towards the side that has more moles of gas to increase the pressure

Question 34

what happens if you increase the concentration of reactants in equilibrium?

Answer 34

the equilibrium will move to the right to use up the reactants (more products)

Question 35

what happens if you increase the concentration of products in equilibrium?

Answer 35

the equilibrium will move to the left to use up products (more reactants)

Question 36

what happens in a titration?

Answer 36

we use an indicator to find the exact volume of acid/alkali needed to neutralise a know volume of acid/alkali

Question 37

how can you make soluble salts?

Answer 37

by reacting an acid with a metal, an insoluble metal hydroxide or a metal carbonate

Question 38

what is the process of making soluble salts?

Answer 38

insoluble substance + acid, = soluble salt (also co2, ho2,) filter the access solid to get a pure solution heat the solution to evaporate the water

Question 39

how can you make insoluble salts?

Answer 39

a precipitation reaction

Question 40

what is the method of making insoluble salts?

Answer 40

1. 1 spatula of lead nitrate + deionised water in test tube, shake. do same thing with sodium chloride in a test tube 2. tip the 2 solutions into a small beaker and give them a good stir. the lead cl should precipitate 3. filter contents in a beaker and take the lead chloride