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Flashcards in Acids And Bases Deck (55):
1

Define a base according to Brønsted-Lowry theory

Proton acceptor

2

Define an acid according to Brønsted Lowry

Proton donor

3

Define a conjugate acid-base pair according to Brønsted Lowry

An acid and base species that differ only by one proton

4

What is the conjugate acid and conjugate base of H2O?

acid - H30+
base - OH-

5

Define PH

-log10[H+]

6

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

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+

7

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

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

8

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

Colour change coincides with sharp rise on graph

9

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

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

10

Define Kw

[H+] [OH-]

11

What is an Arrhenius acid?

Neutral molecule that dissociates in water to form hydrogen ions

12

What is an Arrhenius base?

A neutral molecule that dissociates in water to form hydroxide ions

13

State one limitation of the PH scale

Suitable only for dilute solutions
Only valid in 1-14 range

14

How do you calculate initial concentration with Ka from graph

Use first PH and do from there

15

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

Where it goes vertical
Draw a ruler

16

Refer to PH curve to justify answer of indicator from graph

Range of indicator coincides with vertical part of PH

17

HNO2 + H2O - H3O+ + NO2-

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

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

18

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

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

19

How do you find the conjugate base of an acid?

-1 hydrogen
-1 charge

20

How do you find the conjugate acid of a base?

+1 hydrogen
+1 charge

21

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

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

22

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

i) HSO4-
ii) A-

A- because it’s conjugate acid is weak

23

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

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

24

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

GET IN MOLES PER LITRE - DIVIDE BY MR OF 40 = .005
-log10(.005) = 2.3. BASE = 14-2.3 = 11.7

25

When do acids and bases conduct electricity?

When dissolved in water

26

What are the limitations of the Arrhenius theory?

It only refers to acids and bases dissolved in water

27

What is the advantage of the Brønsted-Lowry theory

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

What occurs when acids react with water itself?

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

29

What is an alkali?

It’s a base that dissolves in water

30

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

Weak
The stronger the acid, the weaker the conjugate base

31

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

HNO3 AND NO3- -> bc they differ from each other by a H+
H20 and H30+ -> differ by h+

32

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

2H20 H30+ + OH-

33

Explain the term monobasic acid

An acid that has one displaceable H atom per molecule

34

What is an acid-base indicator?

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

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

i) HA + H2O -> H30+ + A-
ii) HA + HX -> H2X+ + A-

36

If u have a weak acid indicator what occurs in equilibrium
i) added to an acid
ii) added to base

System will shift to left due to high h+ concentration
System will shift to right due to the OH- ions consume the H+

37

If u have a weak base indicator what occurs in equilibrium
i) added to a base
ii) added to an acid

i) equilibrium shifts to left in excess OH-
ii) equilibrium shifts right as OH- are consumed by H+

38

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

[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

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

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

Limitations of the PH scale

Only works well with dilute aqueous solutions

41

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

4.5 x 10 = 45g per litre
Divide by mr = MOLAR

42

Give examples of strong acids

HCl, H2SO4, HNO3

43

Give examples of weak acids

CH3COOH, HCOOH

44

Give examples of strong bases

NaOH, KOH, Ca(OH)2

45

Give examples of weak bases

NH3 + NH4OH

46

What indicator is used for strong acid and a strong base

Any indicator

47

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

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

48

What indicator is used for a weak acid and strong base

Phenolphthalein [colourless-pink]
[7-10]

49

What indicator is suitable for a weak acid and weak base

No suitable indicator

50

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

Strong acid - weak acid
PH range of indicator lies within PH range of these titrations and give sharp end point

51

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

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

What colour is formed when phenolphtalein is added to
i) acid
ii) base

i) Colourless
ii)Purple/Pink

53

What colour is formed when methyl orange is added to
i) acid
ii) base

i) Red
ii) Yellow

54

What colour is formed when litmus is added to
i) acid
ii) base

i) Red
ii) Blue

55

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

Weak acid v Strong base