Acids and bases

Question 1

what does the pH scale measure?

Answer 1

The pH scale is a measurement of how acidic or alkaline a solution is

Question 2

What pH does a neutral acid and alkaline have?

Answer 2

A neutral substance has a pH of seven
And acid is a substance, with a pH of less than seven
And alkaline have a pH of more than seven

Question 3

What type of ions do acids form in water?

Answer 3

H+ ions
The higher of the concentration of hydrogen ions in the solution, the more acidic it is

Question 4

what type of ions do alkalis form in water?

Answer 4

OH- ions hydroxide ions

Question 5

What is a base?

Answer 5

A base is a substance that reacts with an acid to produce assault and water

Question 6

what is an indicator?

Answer 6

An indicator as a die, that changes colour, depending on whether it’s above or below a certain pH

Question 7

How do we use indicators?

Answer 7

add a few drops of solution that your testing, then compare the The solution goes to a pH chart, such as universal indicator

Question 8

How do you read the results of litmus paperwork?

Answer 8

if the solution goes red, it is acidic
If the solution goes purple, it is neutral
If the solution goes blue, it is alkaline

Question 9

how do methyl orange indicators work?

Answer 9

The solution turns red if acidic
The solution turns yellow when neutral and alkaline

Question 10

how does phenolphthalein work?

Answer 10

It is colourless in acidic or neutral solutions, but turns pink in alkaline solutions

Question 11

what are the reactions between an acid and a base called?

Answer 11

The reaction between an acid and the base is called neutralisation, and it produces a salt and water

Question 12

how can we investigate the neutralisation reaction between calcium oxide?(A bass) and dilute hydrochloric acid

Answer 12

Spot by measuring out a set volume of dilute, hydrochloric acid into a clinical flask and use a puppet or measuring cylinder
Measure out a fixed mass of calcium oxide using a mass balance
Add the calcium oxide to the hydrochloric acid
Wait for the base to react, then record the pH of the solution, either using a pH probe or universal indicator paper
Repeat steps to 4, until all the acids has reacted to the point where you get unreacted calcium oxide, sitting at the bottom of the flask
You can then plot a graph to see how pH changes with a mass of base added.

Question 13

what does it mean when an acid ionises in solution?

Answer 13

This means splitting up to produce hydrogen ions and other ions
E.g.
HCL———->H+ + cl-

Question 14

what is a strong acid, and what are a few examples of them

Answer 14

Strong acids, such as sulphuric, hydrochloric and nitric acid ionised almost completely in water which they tend to have low PHS

Question 15

what is a weak acid, and what are a few examples of them

Answer 15

weak acids, such as ethanolic, citric, and carbonic acids, do not fully ionise in solution, and only a small proportion of acid molecules dissociate into release H+ ions.
The ionisation of a weak acid is reversible, which sets up an equilibrium since only a few of the acids particles release h+ ions

Question 16

What is another word for ionisation?

Answer 16

Dissociation

Question 17

What is formed when an acid reacts with a base?

Answer 17

assault is formed during neutralisation reaction
Salts are ionic compounds
In general hydrochloric acid, produces chloride, salts and sulphuric acid produces sulphate salt, and nitric acid produces nitrate salt

Question 18

What happens when you add an acid and the metal oxide?

Answer 18

Salt +water
2HCL+ CuO—> CuCL2+H2O

Question 19

What does it produce when an acid reacts with a metal hydroxide?

Answer 19

Salt and water
HCL+NaOH——> NaCl + 2H2O

Question 20

What happens when an acid reacts with a metal?

Answer 20

Salt + hydrogen
2HCL+ MG——-> MGCl2 +H2

Question 21

how can you test for hydrogen?

Answer 21

squeaky pop
You can test for hydrogen using a lighted splint
Hydrogen makes a squeaky pop with a lighted splint. The noise comes from the hydrogen burning with oxygen in the air to form water.

Question 22

What do you get when an acid and the metal carbonate react?

Answer 22

salt+ water + carbon dioxide
2HCl + Na2 Cl + H2O+ CO2

Question 23

how can you test to see if a gas is carbon dioxide?

Answer 23

Bubbling lime water through it as the limewater will turn cloudy

Question 24

What are the soluble substances?

Answer 24

Nitrates, chlorides (except silver chloride and lead chloride), sulphates (except lead, barium, and calcium sulphate), common carbonates, and hydroxides for sodium, potassium, and ammonium are generally soluble in water.

Question 25

What are the insoluble substances?

Answer 25

chloride such as silver chloride, and lead chloride
Common sulphates, such as lead barium and calcium sulphate

Question 26

How can you make a pure dry sample of an insoluble salt?

Answer 26

You can use a precipitation reaction, which you need to pick the right two soluble salts and react them together to get your insoluble salt

Question 27

What is the method for precipitation?
Use how to make lead chloride using lead, nitrate and sodium chloride

Answer 27

first, at the spatula of lead nitrate to a test tube and add water to dissolve it
You should use the deionised water to make sure that there are no other ions present
Shake it thoroughly to ensure that all lead nitrate has dissolved then in a separate test tube do the same with one spatula of sodium chloride
Tip the two solutions into a small beaker and give it a good stuff to make sure it’s all mixed together . The lead chloride should precipitate out.
Put a folded piece of filter paper into a filter funnel and stick the funnel into a cornical flask
The contents of the beaker into the middle of the filter paper and make sure that the solution does not go above the filter paper. Otherwise, some of the solid could dribble down the side.
Swell out the beaker with deionised water and tip this into the filter paper to make sure that you get all the precipitate from the beaker
Rinse the contents of the filter paper with deionised water to make sure all the soluble sodium nitrate has been washed away. They just scraped the lead chloride onto a fresh filter paper and leave it to dry.

Question 28

What is titration used for?

Answer 28

soluble salts can be made by reacting and acid with an alkaline
But you can’t tell whether the reaction has finished – there’s no signal that all the acid has been neutralised. You can’t just add an excess of alkaline to the acid because the salt is soluble and would be contaminated by access alkali
Instead, you need to work exactly the right amount of alkaline to neutralise the acid you need to do a titration using an indicator

Question 29

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Answer 29

Measure out a set amount of acid into a conical flask, using epithet and add a few drops of indicator
Slowly, add alkali to the acid using a barrette until you reach the endpoint – this is when the acids Been exactly neutralised and the indicator changes colour
Then carry out the reaction using the exact same volume of alkali and acid, but with no indicator, so the sort won’t be contaminated with indicator
The solution that remains when the reaction is complete, contains salt and water
Slowly, evaporate off some of the water, and then leave the solution to crystallise . Filter off solid and dry – left with pure dry salt.

Question 30

What is electrolysis?

Answer 30

electrolysis is the breaking down of substances, using electricity. An electric current is passed through an electrolyte( a molten or dissolved ionic compound) causing it to decompose

Question 31

in electrolysis, what is oxidation and reduction?

Answer 31

Oxidation is the loss of electrons
Reduction is the gain of electrons
O.I.L.R.I.G

Question 32

where do the positive ions in the electrolytes move?

Answer 32

The cations moved to the cathode (the negative electrode) And are reduced meaning gained elections

Question 33

where do the negative ions in the electrolyte move towards?

Answer 33

The negative and ions move towards the anode( the positive electrode) where they are oxidised

Question 34

what do half equations show?

Answer 34

Half of equations show how electrons are transferred during reactions. They are really useful for sharing what happens at each electrode during electrolysis

Question 35

How do you write a half equation?

Answer 35

first put one of the things being oxidised or reduced on one side of an arrow, and the thing it gets oxidised or reduced to on the other
Balance up the numbers of atoms, just normal equations
Then add electrons (written E-) to one side to balance up the charges

Question 36

What is an electrochemicall cell?

Answer 36

An electrochemical cell is a circuit made up of the unloaded, cathode electrolyte, a power source and the wires that connect the two electrodes

Question 37

how do you set up an electrochemical cell if your electrolytes a solution?

Answer 37

Firstly, get two inert(unreactive) electrodes, e.g. graphite, or platinum electrodes
Clean the surfaces of the electrodes , using some emory paper or sandpaper
From this point, and be careful not to touch the surfaces of the electrodes with your hands – you could transfer grease back onto the strips
Both electrodes into a beaker filled with your electrolyte
Connect the electrode to a power supply, using crocodile, clips and wires. When you turn, the power supply on a circuit will flow through the cell.

Question 38

how do you set up your electro chemical cell if your electrolytes are molten, ionic substance?

Answer 38

put your solid ionic substance(which will become your electrolyte) in the crucible
Hit the crucible with a Bunsen burner until the solids molten. you should do this in a fume cupboard to avoid releasing any toxic fumes into the room
Once the solid molten dip to clean and electrodes into the electrolyte
Then connect the electrodes to a power supply using wires and clips – you should get a current flowing through the cell when you hit the power on

Question 39

why can’t ionic solids be electrolysed?

Answer 39

An ionic solid, can’t be electrolysed because the ions are in a fixed position and can’t move

Question 40

Why can molten ionic compounds be electrolysed?

Answer 40

molten ionic compounds can be electrolysed because the ions can move freely and conduct electricity positive. Metal ions are reduced and metal atoms at the cathode and negative ions are oxidised to atoms or molecules at the anode

Question 41

What are present in aqueous solutions in electrolysis?

Answer 41

H+ and OH-

Question 42

what will be produced at the cathode if metal ions and H+ ions are reacted in an electrolysis aqueous solution

Answer 42

at Cathode H+ plus ions and metal ions are present the hydrogen gas will be produced. If the metal is more reactive than hydrogen. If the metals is less reactive than hydrogen, then a solid layer of pure metal will be produced instead.

Question 43

what will be produced in an aqueous solution if OH- and halide ions are present at the anode?

Answer 43

At the anode, if OH- and the halide ions like Cl2 BR I are present. Molecules of chlorine, bromine and iodine will be formed if no halides or ions are present then oxygen will be formed.

Question 44

what are the four different ions that are present in copper sulphate?

Answer 44

Cu2+ , SO4^-2 , H+ , OH-

Question 45

what happens when you electrolyse copper sulphate solution with inert electrodes?

Answer 45

Copper is less reactive than hydrogen so copper metal is produced at the cathode, which you can see a coating of copper on the electrode
there aren’t any halide ions present, so oxygen and water are produced at the end

Question 46

as the reaction continues during electrolysis, but with copper electrodes, what happens?

Answer 46

as the reaction continues, the mass of the anode will decrease and the mass of the cathode will increase. This is because copper is transferred from the anode to the Cathode.

Question 47

How long would you wait to see a decent change in mass within the electrodes?

Answer 47

30 minutes

Question 48

how can you measure the mass of the electrodes during copper electrolysis

Answer 48

By finding the difference between the masses of the electrodes before, and after the experiment

Question 49

What happens if you increase the current during the reaction?

Answer 49

if you increase the current by adding batteries, you will increase the rate of electrolysis. This means there will be a bigger difference between the mass of the two electrodes after the same amount of time.