Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry GCSE > SC4 - Acids and Alkalis > Flashcards

SC4 - Acids and Alkalis Flashcards

You may prefer our related Brainscape-certified flashcards:
GCSE Geography - AQA flashcards AP® Chemistry flashcards GCSE Religious Studies - Edexcel Route B flashcards GCSE Religious Studies - Eduqas Route A flashcards GCSE Religious Studies - Edexcel Route A flashcards GCSE Religious Studies - Eduqas Route B flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What is concentration?

A

The amount of solute per unit volume. Concentrated acids have lots of H+ ions per unit volume, concentrated alkalis have lots of OH- ions per unit volume.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the pH scale?

A

A measure of the acidity or alkalinity of a substance.

1 2 3 4 5 6 7 8 9 10 11 12 13 14
Acidic Neutral Alkaline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are indicators?

A

Substances that change colour depending on the pH.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What colour is universal indicator in acids, alkalis and neutral?

A

Acids - red
Neutral - green
Alkalis - blue/purple

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What colour is litmus in acids and alkalis?

A

Acids - red

Alkalis - blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What colour is methyl orange in acids and alkalis?

A

Acids - red

Alkalis - yellow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What colour is phenolphthalein in acids and alkalis?

A

Acids - colourless

Alkalis - pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the difference in concentration between an acid of pH1 and pH3?

A

Each time the pH of an acid increases by 1 it has been diluted by a factor of 10. So, pH1 is 10x10 more concentrated than pH3 (x100 difference).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How can you measure pH?

A

Universal indicator can be used then matched to a colour chart.
A pH probe can be used to measure the pH to to 2d.p. . This is better as it removes human error and gives the value to 2d.p. whereas universal indicator will only give a whole number.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a strong acid?

A

Strong acids fully dissociate (split up) when in solution. For example, all molecules of hydrochloric acid (HCl) are spilt into H+ and Cl- ions. This means that strong acids generally have lower pHs as all the molecules produce H+ ions, however this may not always be the case if it is very dilute.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are weak acids?

A

Weak acids only partially dissociate (split up into ions) in solution. For example, only a few ethanoic acid molecules (CH3COOH) split up into CH3COO- and H+, the rest stay the same. Weak acids generally have higher pHs (closer to neutral) as only some molecules produce H+ ions, however this is not always the case as it may be very concentrated.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the equation for the reaction between an acid and a base?

A

Base + acid -> salt + water (BASH2O)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the equation for the reaction between an acid and a metal?

A

Metal + acid -> salt + hydrogen (MASH2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the equation for the reaction between an acid and a metal carbonate?

A

Metal carbonate + acid -> salt + water + carbon dioxide (CASH2OCO2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How would you prepare a soluble salt from an insoluble base?

A

Add an excess of the insoluble base to the acid (you know it’s in excess when it stops dissolving). Filter off the excess then crystallise the salt solution to form crystals of the soluble salt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Core practical - preparing copper sulphate

A
  • measure 20cm3 of dilute sulphuric acid using a measuring cylinder and pour it into a small conical flask.
  • warm the acid in a water bath of 50 degrees
  • add a little copper oxide to the flask and stir
  • if it all reacts, add a little more until it no longer reacts
  • filter and transfer to an evaporating basin
  • heat the solution with a Bunsen burner until around half has evaporated, then take off the heat and leave to cool
  • dry the crystals in an oven.
17
Q

What are acids?

A

Acids are substances which release H+ ions when dissolved in solution.

18
Q

What are alkalis?

A

Alkalis are soluble bases. They release OH- ions when dissolved in solution.

19
Q

Core practical - investigating neutralisation

A
  • Use a measuring cylinder to add 50cm3 of dilute hydrochloric acid to a beaker
  • put a piece of universal indicator paper on a white tile and dip a glass rod into the liquid and tap it on the U.I. paper, wait 30secs and match the colour to a pH colour chart.
  • measure out 0.3g calcium hydroxide power onto a weighing boat
  • add the calcium hydroxide to the beaker and stir then estimate and record the pH
  • repeat 7 times so you have added a total of 2.4g of calcium hydroxide powder.
  • plot a graph with pH on the y axis and mass of calcium hydroxide added on the x axis.
20
Q

Why do acids and alkalis neutralise each other (ionic equation)?

A

H+ + OH- -> H2O

21
Q

How would you carry out a titration?

A
  • use a glass pipette and pipette filler to measure out a fixed volume of alkali and add to a conical flask.
  • fill the burette to the 0.0cm3 mark
  • add a few drops of a suitable indicator (e.g. phenolphthalein) to the alkali
  • open the tap on the burette and swirl the flask as you go, adding the acid more slowly as you near the end point (you know when it’s the end point as the indicator changes colour).
22
Q

How would you obtain a pure, dry salt using titration?

A
  • carry out a titration
  • note the exact volume of acid needed to neutralise the alkali
  • use the burette to add the correct volume of acid without the indicator
  • use crystallisation to obtain the salt.
23
Q

What would you observe when metals react with acids?

A

Effervescence (due to hydrogen gas being released - note you do not actually see the hydrogen), fizzing, bubbles, metal disappears

24
Q

What are the different gas tests?

A

Hydrogen - apply lit split, squeaky pop sound
Oxygen - apply glowing splint, which relights
Carbon dioxide - bubble through limewater, which goes cloudy

25
Q

How do you write ionic equations?

A
  • Write the balanced symbol equation with state symbols
  • split all ionic compounds into their ions (e.g. HCl would be written as H+ + Cl- but H20 would stay H20 as it is covalent).
  • cancel out spectator ions (any ions which appear on both sides of the equation)
  • write out what is left - this is the ionic equation.
26
Q

How do you write half equations?

A

Choose one reactant and show what product it forms. Then, add electrons to one side of the equation to balance the charges.

2H+ + 2e-> H2

27
Q

What are oxidation and reduction reactions?

A

Oxidation is the loss of electrons, reduction is the gain of electrons (OIL RIG). If electrons appear on the right hand side of a half equation, it is oxidation, if they appear on the left hand side, it is reduction.

28
Q

What would you observe in a reaction between a metal carbonate and an acid?

A

Effervescence (due to carbon dioxide being given off), bubbles, metal carbonate disappears

29
Q

What are the solubility rules?

A

Soluble in water:

  • all group 1 and ammonium salts
  • all nitrates
  • most chlorides
  • most sulphates
  • group 1 and ammonium carbonates
  • group 1 and ammonium hydroxides

Insoluble in water:

  • silver, lead chlorides
  • lead, barium, calcium sulphates
  • most carbonates
  • most hydroxides
30
Q

What are precipitation reactions?

A

Reactions in which soluble substances in solution cause an insoluble precipitate to form. In precipitation reactions, the metals ‘swap’ e.g. silver nitrate (aq) + sodium chloride (aq) -> silver chloride (s) + sodium nitrate (aq)

31
Q

How would you prepare an insoluble salt?

A
  • measure out the correct amounts of each solution and mix in a beaker
  • filter the mixture and rinse the beaker with a little distilled water
  • pour a little distilled water over the precipitate in the funnel
  • remove the filter paper containing the precipitate and dry it in a warm oven.

Chemistry GCSE (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions