Acids, Bases, pH

Question 1

What is a Bronsted-Lowry acid

Answer 1

Is a proton donor

Question 2

What is a bronsted-Lowry base

Answer 2

Is a proton acceptor

Question 3

What is a conjugate acid-base pair, give an example with HCL

Answer 3

Contains 2 species that can be interconverted by transfer of a proton

HCL—>H+ + Cl-

In forward direction HCl releases a proton to form conjugate base Cl-
In reverse direction Cl- accepts a proton to form its conjugate acid HCl

Question 4

HCl + OH- = H2O + Cl-
What is acid 1,2 and base 1,2

Answer 4

HCl= acid 1
OH-= base 2
H20= acid 2
Cl-= base 1

Question 5

What is a monobasic acid

Answer 5

An acid that completely dissociates 1 Hydrogen ion per molecule

Question 6

What is a dibasic acid

Answer 6

A molecule that completely dissociates 2 hydrogen ions per molecule

Question 7

What is a tribasic acid

Answer 7

A molecule that completely dissociates 3 hydrogen ions per molecule

Question 8

Redox reactions between metal and acid, give example with zinc

Answer 8

Salt + hydrogen formed

Zn + 2H+ —> Zn2+ + H2(g)

Question 9

Redox reactions between neutralisation of acids with carbonates
Give example with cooper carbonate

Answer 9

Salt + water + CO2 formed

2H+ + CuCO3 —> Cu2+ + H20 + CO2

Question 10

Neutralization of acids with metal oxides
Give example with MgO

Answer 10

Salt + water formed

2H+ + MgO —> Mg2+ + H2O

Question 11

Neutralization of acids with alkalis
Give example with OH-

Answer 11

Salt + water formed

H+ + OH- —> H2O

Question 12

What is the equation for pH with H+
(Equation for pH of a strong acid)

Answer 12

pH= -log[H+]

Question 13

What is the equation for H+ with pH

Answer 13

H+= 10^-pH

Question 14

If a substance has a high value of H+ what will the pH be

Answer 14

A low value

Question 15

If a substance has a high pH what will the concentration of H+ be

Answer 15

A low value

Question 16

What is a strong acid

Answer 16

An acid that completely dissociates in aqueous solution

Question 17

What is a weak acid

Answer 17

An acid that partially dissociates

Question 18

What is the equation for Ka

Answer 18

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

Units= mol dm^-3

Question 19

What is the equation for pKa

Answer 19

pKa= -logKa

Question 20

What is the equation for Ka with pKa

Answer 20

Ka= 10^-pKa

Question 21

If an acid is strong what is the value of Ka and pKa

Answer 21

Ka= large value
pKa= small value

Question 22

If the Ka value is small and pKa value large what is the pH

Answer 22

A weak acid

Question 23

When calculating pH of a weak acid, what 3 approximations do you make

Answer 23

The dissociation of water is negligible- at 25^C= 10^-7moldm^-3, if pH> 6 then H+ then dissociation will be significant compared with dissociation of a weak acid

Assumes that the conc of acid is much greater then H+ concentration at equilibrium

Question 24

How do you calculate pH of a weak acid (CH3COOH)

Answer 24

Ka= [H+] [CH3COO-] / CH3COOH

Ka= [H+]^2 / CH3COOH

H+= (square root) Ka X CH3COOH

pH= -log[H+]

Question 25

What is kW called

Answer 25

Ionic product of water

Question 26

What is the pH of pure water at 25^C

Answer 26

7

Question 27

What is the equation for H+ with Kw and OH

Answer 27

H+= Kw/ OH-

Question 28

What is the equation for Kw with H+ and OH-

Answer 28

Kw= H+ X OH-

Question 29

How to calculate pH of a solution of a strong base
( NaOH with a conc of 0.075)

Answer 29

Convert NaOH into OH- = 0.076(strong mono basic alkali)

Use Kw and OH- to find H+ = H+= Kw/OH- = 1X10^-14/ 0.075 = 1.33X10^-13

pH= -log[H+] = -log(1.33X10^-13) = 12.88

Question 30

What is the value of Kw

Answer 30

10^-14 Mol^2dm^-6

Question 31

How to calculate pH of a weak base
OH-= 4.5X10^-3, at 25^C

Answer 31

pOH= -log[OH]= -log[4.5X10^-3]= 2.34

pH= 14-pOH, pH= 14-2.34, = 11.66

Question 32

What is value of pOH when pH= 0,3,7,10,14

Answer 32

14,11,7,4,0