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Chemistry - New > Acids And Bases > Flashcards

Acids And Bases Flashcards

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1
Q

Define a base according to Brønsted-Lowry theory

A

Proton acceptor

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2
Q

Define an acid according to Brønsted Lowry

A

Proton donor

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3
Q

Define a conjugate acid-base pair according to Brønsted Lowry

A

An acid and base species that differ only by one proton

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4
Q

What is the conjugate acid and conjugate base of H2O?

A

acid - H30+

base - OH-

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5
Q

Define PH

A

-log10[H+]

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6
Q

In terms of hydrogen ions, account for the difference in PH values of .1M of hydrochloric acid and .1M of sulfuric acid

A

HCL is monobasic and therefore each molecule of HCL contains one H+
Sulfuric acid is dibasic and therefore each molecule of sulfuric acid contains two H+

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7
Q

In terms of hydrogen ions, account for the difference in PH values between .1M of hydrochloric acid and .1M of methanoic acid

A

HCL - is monobasic and therefore in each HCL molecule there is one H+
Methanoic acid is dibasic and therefore in each methanoic acid molecule there are two H+ ions

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8
Q

Explain the selection of ur graph in reference to your PH curve

A

Colour change coincides with sharp rise on graph

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9
Q

Distinguish between a strong acid and a weak acid in terms of Arrhenius and Brønsted lowrry

A

Arrhenius
Strong- dissociates completely to give H+ ions
Weak - dissociates slightly to give H+ ions
Brønsted Lowry
Strong acid - readily transfers protons
Weak acid - transfers protons less readily

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10
Q

Define Kw

A

[H+] [OH-]

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11
Q

What is an Arrhenius acid?

A

Neutral molecule that dissociates in water to form hydrogen ions

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12
Q

What is an Arrhenius base?

A

A neutral molecule that dissociates in water to form hydroxide ions

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13
Q

State one limitation of the PH scale

A

Suitable only for dilute solutions

Only valid in 1-14 range

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14
Q

How do you calculate initial concentration with Ka from graph

A

Use first PH and do from there

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15
Q

Make use of PH graph to deduce the volume of a solution required for neutralisation

A

Where it goes vertical

Draw a ruler

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16
Q

Refer to PH curve to justify answer of indicator from graph

A

Range of indicator coincides with vertical part of PH

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17
Q

HNO2 + H2O - H3O+ + NO2-

Explain how the h3O+ / H+ concentration confirms that nitrous acid is a weak acid

A

Concentration of hydronium ions is lower than .2M of nitric acid which means it only slightly dissociates

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18
Q

HIn is a weak acid which dissociates as follows in water
HIn H+ and In-
Green purple

State and explain the colour observed when a few drops of the solution of the indicator is added to NaOH solution

A

Purple - hydroxide ions are removed by hydrogen ions which abuse reaction to shift forward

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19
Q

How do you find the conjugate base of an acid?

A
  • 1 hydrogen

- 1 charge

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20
Q

How do you find the conjugate acid of a base?

A

+1 hydrogen

+1 charge

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21
Q

Distinguish between a weak base and strong base in terms of Arrhenius and Brønsted Lowry

A

Arrhenius -
Strong - dissociates completely to give off hydroxide ions
Weak - dissociates slightly to give off hydroxide ions
Brønsted-Lowry
Strong - accepts protons more readily/good proton acceptor
Weak - accepts protons less readily / bad proton acceptor

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22
Q

What is the conjugate base of
i) sulfuric acid
ii) weak acid HA
And which of these bases are stronger?

A

i) HSO4-
ii) A-

A- because it’s conjugate acid is weak

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23
Q

Explain by giving a balanced equation for its dissociation in water that the conjugate base of sulfuric acid is itself an acid

A

HSO4- + H20 - SO4^2- + H30+

24
Q

The concentration in an aqueous solution of sodium hydroxide is .2g per litre. Calculate its PH

A

GET IN MOLES PER LITRE - DIVIDE BY MR OF 40 = .005

-log10(.005) = 2.3. BASE = 14-2.3 = 11.7

25
Q

When do acids and bases conduct electricity?

A

When dissolved in water

26
Q

What are the limitations of the Arrhenius theory?

A

It only refers to acids and bases dissolved in water

27
Q

What is the advantage of the Brønsted-Lowry theory

A

Not restricted to water based acids and bases
It allows gaseous reactions
It allows for the amphoteric nature of water [can act as an acid and as a base]

28
Q

What occurs when acids react with water itself?

A

H+ ion creates a dative bond with the lone pairs on the water’s oxygen atom to from H30+

29
Q

What is an alkali?

A

It’s a base that dissolves in water

30
Q

If there’s a strong acid, is the conjugate bass weak or strong?

A

Weak

The stronger the acid, the weaker the conjugate base

31
Q

Identify the conjugate acid-base pairs in the following reaction
HNO3 + H20 = H30+ + NO3-

A

HNO3 AND NO3- -> bc they differ from each other by a H+

H20 and H30+ -> differ by h+

32
Q

Give the equation/expression for when water self ionises to a small extent

A

2H20 H30+ + OH-

33
Q

Explain the term monobasic acid

A

An acid that has one displaceable H atom per molecule

34
Q

What is an acid-base indicator?

A

A weak base or acid which in a solution has one colour at a particular PH and a different colour at a different PH

35
Q

i) Write an equation for the reaction that takes place between a strong monobasic acid and water
ii) Write also an equation for the reaction takes place when a weak monobasic acid accepts a proton from the strong monobasic acid HA

A

i) HA + H2O -> H30+ + A-

ii) HA + HX -> H2X+ + A-

36
Q

If u have a weak acid indicator what occurs in equilibrium

i) added to an acid
ii) added to base

A

System will shift to left due to high h+ concentration

System will shift to right due to the OH- ions consume the H+

37
Q

If u have a weak base indicator what occurs in equilibrium

i) added to a base
ii) added to an acid

A

i) equilibrium shifts to left in excess OH-

ii) equilibrium shifts right as OH- are consumed by H+

38
Q

The value of Kw at 25 degrees celsius is 1.0 x 10^-14

Show that the PH of pure water is 7.0 at 25 degrees Celsius

A 
[H+] = [OH-]
[H+]2 = 1.0 x 10^-14 
square root both sides
H+ = 1.0 x 10^-7
-log10(1.0 x 10^-7)
7
39
Q

Explain how an acid-base indicator which is itself a weak acid + may be represented as HX, functions

A

It is represented as
HX -> H+ + X-
In an acid, equilibrium shifts to the left as there is more of a concentration of H+ and gives the molecules colour
In a base, the equilibrium shifts to the right as OH- ions are consumed by H+ which gives the colour of molecules

40
Q

Limitations of the PH scale

A

Only works well with dilute aqueous solutions

41
Q

How do u get to M/L from 4.5g per 100cm^3

A

4.5 x 10 = 45g per litre

Divide by mr = MOLAR

42
Q

Give examples of strong acids

A

HCl, H2SO4, HNO3

43
Q

Give examples of weak acids

A

CH3COOH, HCOOH

44
Q

Give examples of strong bases

A

NaOH, KOH, Ca(OH)2

45
Q

Give examples of weak bases

A

NH3 + NH4OH

46
Q

What indicator is used for strong acid and a strong base

A

Any indicator

47
Q

What indicator is used for a strong acid and weak base?

A

Methyl orange [red-yellow] [3-7]

48
Q

What indicator is used for a weak acid and strong base

A

Phenolphthalein [colourless-pink]

[7-10]

49
Q

What indicator is suitable for a weak acid and weak base

A

No suitable indicator

50
Q

The indicator changes colour in the PH range 3.7-5.7. State a type of acid-base titrations for which it would be suitable and justify your answer

A

Strong acid - weak acid

PH range of indicator lies within PH range of these titrations and give sharp end point

51
Q

Explain how an acid-base indicator represented by XOH which itself is a weak base, functions

A

Addition of acid removes the OH- ions as equilibrium shifts to right and colour B dominates
Addition of base increases concentration of OH- ions on RHS side of equation, shifting equilibirum to left and colour A dominates

52
Q

What colour is formed when phenolphtalein is added to

i) acid
ii) base

A

i) Colourless

ii) Purple/Pink

53
Q

What colour is formed when methyl orange is added to

i) acid
ii) base

A

i) Red

ii) Yellow

54
Q

What colour is formed when litmus is added to

i) acid
ii) base

A

i) Red

ii) Blue

55
Q

What titration is used when indicator changes within range of PH 8-10

A

Weak acid v Strong base

Chemistry - New (27 decks)

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