Acids and Bases

Question 1

Bronsted and Lowry def

Answer 1

An acid is a proton donor, a base is a proton acceptor
Proton- H+ ——> H+ = no electron so proton only

Question 2

All the amphiprotic compounds are amphoteric and vice versa.

Answer 2

False.
Amphiprotic substances having both H+ ions to donate and ability to accept protons are amphoteric- can react with both acid and bases but not all amphoteric substances are amphiprotic

Question 3

Hydrogen gas is evolved when metals react with nitric acid

Answer 3

False
due to its strong oxidizing properties, the nitric acid oxidizes the hydrogen to water and hence hydrogen gas is not evolved

Question 4

Neutralization reactions to produce salt from acids and bases are———

Answer 4

Exothermic

Question 5

How do the indicators change the color?

Answer 5

They give info about a change in the environment . They change color according to the change in H+ in the solution. They are weak acids and bases whose conjugates have different color.

Question 6

Three types of indicators

Answer 6

Litmus paper
Methyl orange
Phenolphthalein

Question 7

Color of litmus in acid

Answer 7

Pink

Question 8

Color of litmus in alkali

Answer 8

Blue

Question 9

Color of methyl orange in acid

Answer 9

Red

Question 10

Color of methyl orange in alkali

Answer 10

Yellow

Question 11

Color of phenolphthalein in acid

Answer 11

Colourless

Question 12

Color of phenolphthalein in alkali

Answer 12

Pink

Question 13

Universal indicator

Answer 13

A mixture of several indicators together, they change color across a range of different acids and alkalis

Question 14

Standard solution is the ———

Answer 14

Solution with the known conc

Question 15

pH is a temperature dependent measurement

Answer 15

True

Question 16

What happens to the pH of an acid when 10 cm3 of it is added to 90 cm3 of water?

Answer 16

pH increases by 1 unit

Question 17

Strength of an acid or base is determined by ———

Answer 17

Disssoctiation constant of acids and bases
Ka and Kb
KA myr ——> stronger acid
Kb myr———> stronger base

Question 18

Strong bases are good proton acceptors; they react to form conjugates that do not show acidic properties. Weak bases are poor proton acceptors; they react to form conjugates with stronger acidic properties than the conjugates of strong bases. Base ionization reactions favour the production of the weaker conjugate.

Answer 18

The strength of an acid or base is therefore a measure of how readily it dissociates in aqueous solution. This is an inherent property of a particular acid or base, dependent on its bonding. Do not confuse acid or basic strength with its concentration, which is a variable depending on the number of moles per unit volume, according to how much solute has been added to the water. Note, for example, it is possible for an acid or base
Strong acids and strong bases ionize almost completely in solution; weak acids and weak bases ionize only partially in solution.
In writing the ionization reactions of weak acids and bases, it is essential to use the equilibrium sign.

Question 19

Why is C2H5NH2 weak base?

Answer 19

Note that amines such as ethylamine, C2H5NH2, can be considered as organic derivatives of NH3 in which one of the hydrogen atoms has been replaced by an alkyl (hydrocarbon) group.

Question 20

Ligands

Answer 20

Ligands, as donors of lone pairs, are therefore acting as Lewis bases. For example, Cu2+ in aqueous solution reacts as follows:
Cu2+(aq) + 6H2O(l) → [Cu(H2O)6]2+(aq)
Typical ligands found in complex ions include H2O, CN–, and NH3.

Question 21

In the equal volumes, the strong acid produces more ———

Answer 21

H+ ions
Strong base——> more OH- ions

Question 22

the higher the value of Ka for the acid, the——-the value of Kb for its conjugate base. In other words, stronger acids have ———conjugate bases, and vice versa

Answer 22

Lower
Weaker

Question 23

There are two main types of buffer solution – acidic buffers that maintain the pH at a value ———and basic buffers that maintain the pH at a value———

Answer 23

Less than 7
Greater than 7

Question 24

Dilution cannot change pH of the solution but can alter the ———

Answer 24

Buffering capacity by altering the molar concentrations of its components

Question 25

Are the salts neutral after reacting with acid and bases

Answer 25

Not always, Their pH in solution depends on whether extent their ions, which are conjugate acids and bases, react with water and hydrolyse it, releasing H+ or OH– ions. Weak acid and weak base——> ph not known Strong acid and weak base——> pH less than 7 Weak acid and strong base——> pH greater than 7 Strong acid and strong base——> pH neutral

Question 26

Fe(OH)3 is a _____ base

Answer 26

Weak

Question 27

Indicator molecules are ————

Answer 27

Weak acids and bases in which dissociated and undissociated forms have different colors.

Question 28

Indicator changes shapes when their ———— is equal to ———

Answer 28

PKa or pKb is equal to pH Remember indicators are also weak acids and bases. So , half the equivalence point ——> they have equal amount of acids or bases and their salts(buffer). This is at equilibrium.= end point Increasing H+——> equilibrium will shift so is the same for adding bases . It follows that different indicators, having different pK values, will have different end-points and so will change colour at different pH values.

Question 29

How can indicators be used in titrations?

Answer 29

When the end points of INDICATORS coincide the equivalent points in titration ——> indicators change colors

Question 30

———- is used for acidic titrations strong acid and weak base

Answer 30

Methyl orange. Red to yellow Bromophenol blue yellow to blue

Question 31

———— indicator is used for basic titrations ( weak acid and strong base )

Answer 31

Phenolphthalein colorless to pink Phenol red yellow to red

Question 32

Strong acid + strong base titration indicator

Answer 32

Phenolphthalein or methyl orange

Question 33

Rain water is——-

Answer 33

Acidic at a pH of 5.6

Question 34

How do you produce sulphuric aid from sulphur diocxide

Answer 34

2SO2+ O2——-> 2SO3 SO3+H2O———> H2SO4

Question 35

Which acid is stronger HNO2 or HNO3

Answer 35

HNO3 Why? For oxyacids, the acid with greater number of oxygen is the stronger acid

Question 36

HCLO4, HCLO3, HCLO2, HCLO4* Which is the stronger acids?

Answer 36

HCLO4 look for the oxidation states of central atom. The higher the oxidation number. The more acidic are the oxyacids

Question 37

Which base is stronger? NH3 or CH3CH2NH2

Answer 37

CH3NH2

Question 38

Which acid is stronger ? HBr or HI?

Answer 38

HI HI>HBr>HCl>HF> H2O> NH3> CH3COOH Increases down the group due to the size increase Increases across the period because the polarity of the bonds increases thus the order of increasing acidity

Question 39

Which acid is stronger? HCL0 or HIO

Answer 39

For oxyacids HCLO

Question 40

Which of the following is weak? HCl H2SO4 HNO3 HF HCLO4

Answer 40

HF

Question 41

Which base is stronger. SH- and NO2- ? Ka of NO2- is greater than SH-

Answer 41

SH-

Question 42

HCl HBr HI HF which are strong acids

Answer 42

HCl HBr HI HF is weal

Question 43

H2SO3 HClO HNO2 HCN what kinds of acids are they?

Answer 43

They are weak.

Question 44

If we put HF in water, the resulting soultion will be ———

Answer 44

Basic HF+H2O ——> F- + H3O+

Question 45

Al is ——— in Aqueous solution

Answer 45

These ions are not just loosely solvated by water molecules when dissolved instead they are covalently bonded to a fixed number of water molecules to yield a complex ion.

Question 46

Monoprotic and polyprotic definition

Answer 46

Monoprotic acid- can only lose one proton Polyprotic- can lose several protons Polyprotic acids become LESS acidic as they lose more protons

Question 47

CH3COOH is the —— protic acid

Answer 47

Monoprotic

Question 48

Each successive ionization energy of multiport is acids often decrease by a factor of ——

Answer 48

10*5 to 10*6

Question 49

Monoprotic and diprotic bases

Answer 49

Can accept one proton That can accept two protons

Question 50

The pH of a buffer solution depends on the ratio of the concentration of the acid and the concentration of its conjugate base. If this does not change very much, the pH changes very little.

Answer 50

In unpolluted regions of the Earth, rainwater has a pH of 5.7. This is because carbon dioxide dissolves in the rainwater to form a dilute solution of the weak acid carbonic acid, H2CO3. This acid and its conjugate base, HCO3–, act as a buffer solution. It minimises changes in pH if very small amounts of acid or alkali are added to the rainwater. But in regions where there is pollution caused by the emission of acidic oxides of nitrogen and sulfur, the pH of the rainwater falls to around 4. The rainwater can no longer act as a buffer because the concentrations of the H2CO3 and HCO3– are not high enough to cope with the large amounts of acidic pollution involved. No buffer solution can cope with the excessive addition of acids or alkalis. If very large amounts of acid or alkali are added, the pH will change significantly