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Chemistry (My Flashcards) > SC8 - Acids and Alkalis > Flashcards

SC8 - Acids and Alkalis Flashcards

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1
Q

SC8a - What are alkalis a source of in solution?

A

OH- ions

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2
Q

SC8a - What are the tests for carbon dioxide?

A

bubble the gas through limewater (calcium hydroxide solution); the limewater turns milky if CO2 is present.

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3
Q

SC8a - What are the tests for hydrogen?

A

You can safely test for small amounts of hydrogen gas by holding a splint over the test tube that the hydrogen was collected in. If there is hydrogen the result is a squeaky pop sound as the hydrogen reacts with oxygen in the air in a small explosion.

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4
Q

SC8a - What colour is litmus in acidic solutions?

What colour is litmus in alkaline solution?

A

Red in acidic solutions

Blue when in alkaline solutions

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5
Q

SC8a - What colour is methyl orange in acidic solution?

What colour is methyl orange in alkaline solution?

A

Red in acid

Yellow in alkaline

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6
Q

SC8a - What colour is phenolphthalein in acidic solution?

What colour is phenolphthalein in alkaline solutions?

A

Colourless in acidic solutions

Pink in alkaline solution

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7
Q

SC8a -What are acids a source of in solution?

A

H+ ions

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8
Q

SC8b - How can you test the acidity of a solution?

A

Using universal indicator

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9
Q

SC8b - How do you calculate concentration?

A

Concentration = amount (g)/volume (dm3)

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10
Q

SC8b - How do you make a solution more concentrated?

A

Add more solute / Evaporate some water

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11
Q

SC8b - How do you make a solution more dilute?

A

Add more water

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12
Q

SC8b - What is a base?

A

A substance that reacts with an acid to make salt and water only

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13
Q

SC8b - What is the chemical formula for hydrochloric acid?

A

HCl

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14
Q

SC8b - What is the chemical formula for nitric acid?

A

HNO3

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15
Q

SC8b - What is the chemical formula for sulfuric acid?

A

H2SO4

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16
Q

SC8b - Why do strong acids have a lower pH than weak acids?

A

Strong acids completely dissociate into H+ ions when in solution; whereas weak acids only partially dissociate into H+ ions. This means there is a higher concentration of H+ ions in the strong acids, therefore they have a lower pH

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17
Q

SC8b -If the pH increases by 1; what happens to the concentration of hydrogen ions?

A

Decreased by a factor of 10

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18
Q

SC8c - How can soluble salt be made from acid and alkalis?

A

In an neutralisation reaction between an acid and an alkali. The end point of this reaction is found using an indicator. The salt can be obtained from the solution by evaporation

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19
Q

SC8c - How do you convert cm into dm?

A

divide by 1000

20
Q

SC8c - Represent a neutralisation reaction in an equation

A

H+ + OH- —> H20

21
Q

SC8c CP - Describe how to prepare a soluble salt from an acid and base

A

1) Add excess base
2) Warm bath
3) Filter to remove unreacted solid
4) Heat to evaporate water and concentrate the salt solution
5) Leave to evaporate water slowly for crystallization to occur

22
Q

SC8c CP - Why; when making copper sulfate; do we add the metal oxide in excess?

A

To ensure all the acid reacts

23
Q

SC8c- How can soluble salt be made from acids and metals?

A

In a reaction; an acid and a metal makes a salt and a hydrogen.

24
Q

SC8d - What are spectator ions?

A

Ions that do not change during the reaction

25
Q

SC8e - Describe titration experiment

A
  • Use a pipette to measure out 25cm³ of sodium hydroxide and empty this solution into a conical flask
  • Place the conical flask on a white tile (So you can see the colour change later on)
  • Wash out a burette with hydrochloric acid and fill it up to top with this
  • . Record the inital reading on the burette (from the bottom on the meniscus)
  • Add a few drops of indicator (methyl orange or phenolphthalein) to the conical flask and move this and the white tile under the burette
  • Open the tap of the buretted letting the acid flow through.
  • Constantly swirl the flask
  • When you first see a colour change, slow down the tap
  • For phenolphthalein this will be pink to colourless; For methyl orange this will be yellow to red
  • Once the colour has changed and won’t change back, stop the tap and read the value on the burette (from the bottom of the meniscus)
  • Work out how much acid has been used
  • Repeat multiple times and take an average of the concordant results
26
Q

SC8e - How do we make a pure dry salt from 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 this time
  • Evaporate water from solution formed, crystallisation
27
Q

SC8e - What is a buret?

A

A long; narrow; graduated tube used to add titrate

28
Q

SC8e - What is a stopcock?

A

A small tap that is used to control the flow of the titrate during titration

29
Q

What metals react steadily with dilute acids?

A

Metals in the middle of the reactivity series such as magnesium or zinc

30
Q

SC8f - State the general equation for the reaction between an acid and a metal carbonate

A

metal carbonate + acid –> salt + water + carbon dioxide

31
Q

SC8f - What is a reduction reaction?

A

gain of electrons

32
Q

SC8f - What is an oxidation reaction?

A

loss of electrons

33
Q

SC8f - What is effervescence?

A

rapid escape of a gas from a liquid

34
Q

SC8f - What metals do not react with dilute acids?

A

Copper; Silver

35
Q

SC8f - What metals react explosively with dilute acids?

A

Potassium; Sodium

36
Q

SC8g - Describe the steps required to produce a pure; dry sample of an insoluble salt from two soluble salts

A
  • Wear eye protection
  • Mix the two solutions in a beaker, then filter
  • Rinse the beaker with a little distilled water and pour this thorugh the funnel
  • Pour a little distilled water over the precipitate in the funnel
  • Carefully remove the filter paper containing the precipitate and dry it in a warm oven
37
Q

SC8g - How can soluble salt be made from ammonia solution?

A

By reacting ammonia solution with an acid; ammonium salt and water are produced.

38
Q

SC8g - How can we check whether a precipitate will form?

A

By checking the solubility of the products. If both products are soluble; no precipitate will form.

39
Q

SC8g - What are ammonium salts used for?

A

fertilisers

40
Q

SC8g - What carbonates are soluble?

A

sodium; potassium; ammonium

41
Q

SC8g - What chlorides are insoluble?

A

Silver and lead

42
Q

SC8g - What happens when two solutions containing soluble salts react together?

A

The metals from the salts swap

43
Q

SC8g - What hydroxides are soluble?

A

sodium; potassium; ammonium

44
Q

SC8g - What is a precipitation reaction?

A

When two soluble substances react together to make a product which is insoluble (the precipitate)

45
Q

SC8g - What substances are generally insoluble?

A

Most carbonates most hydroxides

46
Q

SC8g - What substances are generally soluble?

A

all common sodium,pottassium and ammonium salts all nitrates most chlorides most sulfates

47
Q

SC8g - What sulfates are insoluble?

A

Lead; barium and calcium

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