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Science - continued > Acids and Alkalis > Flashcards

Acids and Alkalis Flashcards

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1
Q

Why are hazard symbols useful?

A

They inform us of the dangers of a substance and indicate the precautions needed to be taken whilst handling them

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2
Q

What is the neutral pH

A

7 (below is acid and above is alkali)

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3
Q

How can the pH of a solution be found?

A

Using indicators that change colour depending on the pH

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4
Q

What is universal indicator

A

made of a mixture of different indicators and produces a range of colours depending on the pH

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5
Q

What colour do the following indicators turn in acid:
litmus paper
methyl orange
phenolphthalein

A

red
red
colourless

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6
Q

what colour do the following indicators turn in alkaline:
litmus paper
methyl orange
phenolphthalein

A

blue
yellow
pink

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7
Q

What is an ion and what has to happen in order for them to become positive or negative ions?

A

Ion is an atom that has become charged by losing or gaining electrons. Losing electrons make positive ions (cations) and gaining electrons make negative ions (anions)

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8
Q

What is a polyatomic ion?

A

Covalently bonded set of two or more atoms

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9
Q

How are polyatomic ions formed?

A

when small groups of atoms which are held together by covalent bonds, lose or gain electrons such as OH-

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10
Q

What do acids and alkalis produce when they are dissolved in water?

A

Acids-Hydrogen ions (H+)

Alkalis-Hydroxide ions (OH-)

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11
Q

What does a high concentration of hydrogen or hydroxide ions mean?

A

It means that the concentration of the solution will be higher meaning that the pH will lower for acids and increase for alkalis. The solutions will become more acidic or alkaline.

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12
Q

What ions do neutral solutions contain?

A

low, equal amounts of hydrogen and hydroxide ions

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13
Q

What does a concentrated solution contain compared to a dilute solution?

A

concentrated- lots of dissolved solute

dilute- not much dissolved solute

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14
Q

How do you calculate the concentration?

A

amount dissolved/volume of solution

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15
Q

What happens to the pH if the concentration of hydrogen ions is increased or decreased?

A

If the concentration of hydrogen ions increases by a factor of 10, the pH decreases by 1 and if the concentration of hydrogen ions decreases by a factor of 10, the pH increases by 1

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16
Q

What is the formula for sulfuric acid?

A

H2SO4

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17
Q

What is the formula for nitric acid?

A

HNO3

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18
Q

What is the alkali for NaOH

A

Sodium hydroxide

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19
Q

What is the formula for calcium hydroxide

A

Ca(OH)2

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20
Q

Give three strong acids

A

Nitric acid, hydrochloric acid, sulfuric acid

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21
Q

What happens to the molecules in strong acids

A

they dissociate (break up) into ions when they dissolve in water and produce high concentrations of hydrogen ions

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22
Q

Give an example of a weak acid and say why they are weak

A

Boric acid

they do not dissolve completely into ions

23
Q

What do the chemical properties of an acid depend on?

A

Its concentration and the type of acid

24
Q

What is a base?

A

Substances that react with acids to form a salt and water only

25
Q

What are all metal oxides?

A

Bases e.g magnesium oxide

26
Q

What happens to the ions during neutralisation?

A

hydrogen ions from the acid combine with the oxide ions in the metal oxide and form water which removes the hydrogen ions and makes the acid more neutral

27
Q

What would a neutralisation reaction of magnesium oxide and hydrochloric acid create?

A

Magnesium chloride and water

28
Q

How do you prepare a soluble salt?

A
  1. excess base is added to the acid to make sure the acid is used up
  2. mixture is warmed to speed up the process
  3. mixture is filtered to remove the unreacted solid from the solution
  4. the filtrate is heated over a bunsen burner and crystallisation occurs to evaporate the water
  5. the crystals that are left are the soluble salt
29
Q

Are all bases soluble in water?

A

No, a soluble base is called an alkali

30
Q

Give an example of a metal hydroxide that is insoluble

A

Copper hydroxide

31
Q

What are two bases that are soluble (alkalis)?

A

sodium hydroxide (and other group 1 hydroxides) and calcium hydroxide (and other group 2 hydroxides)

32
Q

Why does the formula for metal hydroxides change when it is a group 2 hydroxide rather than a group 1 hydroxide

A

The formula for group 1 hydroxide is MOH (M being in the metal’s chemical symbol)
the formula for group 2 hydroxides is M(OH)2 because the charge of metals in group 2 have a charge of 2+ and so you would need 2 OH- ions to balance out the compound

33
Q

What happens when an alkali is added to an acid

A

It neutralises and the pH increases and if enough alkali is added, the pH exceeds 7

34
Q

Why is it important to have a neutral acid before evaporating water in a neutralisation experiment?

A

You can contaminate the salt with the excess of one reactant

35
Q

How can you obtain a neutral solution

A

Adding enough of an acid or alkali to the right proportions using a titration

36
Q

Why shouldn’t you use a measuring cylinder when measuring out the alkali in the conical flask (titrations)?

A

Because it is not as accurate as a volumetric pipette

37
Q

What is an end-point in a titration?

A

When the indicator changes colour

38
Q

What indicators should you use when doing a titration and why?

A

Methyl orange or phenolphthalein because they have sharp changing points so it’s easy to record when it happens

39
Q

How do you make pure dry salt using titration?

A
  • carry out a titration
  • record the exact volume of acid needed to neutralise the alkali
  • use the burette to add the correct volume of acid without the indicator
  • evaporate the water from the solution formed
40
Q

How do metals in the middle of the reactivity series react with dilute acids?

A

steadily

41
Q

What are spectator ions

A

Ions from chemicals that do not change in a reaction

42
Q

What is formed when acids react with metal carbonates

A

salt, water and a carbon dioxide (bubbles of carbon dioxide are formed)

43
Q

How do you test for hydrogen?

A

Put a lighted splint in a test tube of hydrogen and a squeaky pop will be heard as hydrogen is flammable

44
Q

How is carbon dioxide and water created in metal carbonate and acid reaction?

A

The hydrogen ions from the acid react with the oxygen ions in the carbonate and the carbon and oxygen make carbon dioxide

45
Q

What is a precipitation reaction?

A

soluble substances in solutions cause an insoluble precipitate to form

46
Q

are all common sodium, potassium and ammonium salts soluble or insoluble in water?

A

Soluble

47
Q

Are all nitrates soluble or insoluble in water?

A

Soluble

48
Q

Which chlorides are INSOLUBLE in water?

A

Silver and lead chlorides

49
Q

Which sulfates are INSOLUBLE in water?

A

Lead, barium and calcium sulfates

50
Q

Which carbonates are SOLUBLE in water?

A

sodium, potassium and ammonium carbonates

51
Q

Which hydroxides are SOLUBLE in water?

A

sodium, potassium and ammonium carbonates

52
Q

What is the test for carbon dioxide

A

Using limewater, which produces a white precipitate of calcium carbonate when carbon dioxide is present

53
Q

Will a precipitate form if both salts are soluble in a reaction?

A

No

54
Q

How do you make a pure dry sample of an insoluble salt from two soluble salts

A
  • wear eye protection
  • mix the two solutions in a beaker and filter
  • rinse the beaker with distilled water and pour through the funnel
  • rinse the precipitate with distilled water
  • remove the filter paper from the funnel and let it dry in an oven

Science - continued (9 decks)

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