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AQA Chemistry > Acids > Flashcards

Acids Flashcards

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1
Q

Give the definition of an acid

A

Acid – A compound that dissolves in water to produce hydrogen ions (H+)

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2
Q

Give the definition of a base

A

Base – A substance that reacts with acid producing a salt and water.

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3
Q

Give the definition of an alkali

A

Alkali – Soluble bases which dissolve in water to produce hydroxide ions OH-

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4
Q

Give the definition of neutralisation

A

Neutralisation - H+ (aq) + OH-(aq) -> H2O(l)

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5
Q

Give the definition of monoprotic

A

Monoprotic – 1 mole of acid produces 1 mole of H+ ions.

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6
Q

Give the definition of diprotic

A

Diprotic – 1 mole of acid produces 2 moles of H+ ions.

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7
Q

Give the definition of a Hydonium ion or hydroxonium ion or oxonium ion.

A

Hydonium ion or hydroxonium ion or oxonium ion – H3O+. It is the ion formed when acids react with water.

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8
Q

Give the definition of a buffer

A

Buffer – solutions that can resist changes in pH when small quantities of acid or base are added.

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9
Q

Give the definition of a Bronsted-Lowry acid

A

A Bronsted-Lowry acid is a proton donor.

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10
Q

Give the definition of a Bronsted-Lowry base

A

A Bronsted-Lowry base is a proton acceptor.

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11
Q

What happens to strong bases in aqueous solution?

A

Strong acids (HCl, H2SO4, HNO3) and bases (NaOH, KOH) completely dissociate in aqueous solution.

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12
Q

What happens to weak bases in aqueous solution?

A

Weak acids and bases are slightly dissociated in aqueous solution.

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13
Q

How do you calculate the new concentration of a solution?

A

New concentration of a solution = amount in moles of

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14
Q

What is the equation for pH?

A

pH = -log10[H+]

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15
Q

What is the equation for [H+]?

A

[H+] = 10(-pH)

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16
Q

What is the equation for Kw?

A

Kw=[H+] [OH-] units mol2dm-6

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17
Q

At 25oC what does Kw equal?

A

At 25oC Kw = 1.00 x 10-14

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18
Q

In pure water how would you calculate [H+]?

A

In pure water [H+] = √Kw

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19
Q

What is the equation for pKw?

A

pKw = -log10Kw (14 at 25oC)

20
Q

What is the equation for pOH?

A

pOH = log10 [OH-]

21
Q

What is the link between pOH and pH?

A

pOH + pH = pKw

22
Q

Give the equilibrium equation for the dissociation of HA.

A

HA H+ + A-

23
Q

What is the equation for Ka?

A

Ka = [A-] [H+] /[HA]

24
Q

What is the equation for pKa?

A

pKa = -log10[Ka]

25
Q

How do you work out the concentration of a weak acid?

A

[Weak acid]=[H+]2 / Ka

26
Q

What is an acidic buffer formed from?

A

Formed from weak acid and its salt

27
Q

What happens when you add acid to an acidic buffer solution?

A

When small amount of acid is added extra H+ ions are added.

28
Q

What happens to the position of equilibrium of an acidic buffer solution?

A

The position of equilibria moves to the LEFT to remove the H+ ions.

29
Q

What happens to the pH of an acidic buffer solution?

A

This keeps the pH almost constant.

30
Q

What happens to a buffer when a base is added?

A

When a small amount of base is added extra hydroxide OH- ions are added.

31
Q

How are the hydroxide ions removed?

A

The hydroxide ions react with the hydrogen ions removing some of the H+ ions.

32
Q

What happens to the position of equilibrium if bases are added and why?

A

The position of equilibrium moves to the RIGHT to replace the H+ ions.

33
Q

What happens to the pH of a buffer when bases are added?

A

This keeps the pH almost constant.

34
Q

What is an acidic buffer formed from?

A

Basic buffers

35
Q

Give the equation for the dissociation of a basic buffer.

A

B + H+ BH+

36
Q

What happens when you add acid to a basic buffer solution?

A

When small amount of acid is added extra H+ ions are removed as they react with the base B.

37
Q

What happens to the position of equilibrium of a basic buffer solution?

A

The position of equilibrium moves to the RIGHT.

38
Q

What happens to a basic buffer when a base is added?

A

When a small amount of base is added extra hydroxide OH- ions are added.

39
Q

How are the hydroxide ions removed?

A

The hydroxide ions react with the hydrogen ions in the buffer removing some of the H+ ions.

40
Q

What happens to the position of equilibrium if bases are added to a basic buffer and why?

A

The position of equilibrium moves to the LEFT to replace the H+ ions

41
Q

What pH range does Thymol blue work over and what is the colour change in acid and in alkali?

A

Thymol blue 1.20-2.80 red – yellow (acid – alkali)

42
Q

What pH range does Methyl orange work over and what is the colour change in acid and in alkali?

A

Methyl orange 3.10-4.40 red – yellow

43
Q

What pH range does Methyl red work over and what is the colour change in acid and in alkali?

A

Methyl red 4.40-6.20 red – yellow

44
Q

What pH range does Bromothymol blue work over and what is the colour change in acid and in alkali?

A

Bromothymol blue 6.00-7.60 yellow – blue

45
Q

What pH range does Phenolphthalein work over and what is the colour change in acid and in alkali?

A

Phenolphthalein 8.30-10.00 colourless – pink.

AQA Chemistry (13 decks)

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