2.3 acid-base and redox reactions

Question 1

strong acids will:

Answer 1

fully dissociate in solution

Question 2

acid-base titration calculations: Neutralisation calculation

26.25.0 cm3 of 0.050 dm-3 sodium carbonate was completely neutralised by 20.00 cm3 of dilute hydrochloric acid.

Calculate the concentration in mol dm-3 of the hydrochloric acid.

Answer 2

Step 1: Write the balanced symbol equation
Na2CO3 + 2HCl → 2NaCl + H2O + CO2

Step 2: Calculate the amount, in moles, of sodium carbonate reacted by rearranging the equation for amount of substance (mol) and dividing the volume by 1000 to convert cm3 to dm3amount (Na2CO3) = 0.025 dm3 x 0.050 mol dm-3 = 0.00125 mol

Step 3: Calculate the moles of hydrochloric acid required using the reaction’s stoichiometry
1 mol of Na2CO3 reacts with 2 mol of HCl, so the molar ratio is 1 : 2 Therefore 0.00125 moles of Na2CO3 react with 0.00250 moles of HCl

Step 4: Calculate the concentration, in mol dm-3, of hydrochloric acid using conc = mol/vol = 0.0025/0.0200concentration (HCl) (mol dm-3) = 0.125 mol dm-3

Question 3

weak acids will:

Answer 3

partially dissociate in solution

Question 4

strong acid examples:

Answer 4

HCl
HNO3
H2SO4

Question 5

weak acid examples:

Answer 5

HCOOH
CH3COOH

Question 6

strong base examples:

Answer 6

• NaOH
• KOH
• Ba(OH)2

Question 7

weak base examples:

Answer 7

• NH3
• CH3
• NH2

Question 8

acid + metal →

Answer 8

salt + hydrogen

Question 9

acid + metal oxide →

Answer 9

salt + water

Question 10

acid + metal hydroxide

Answer 10

salt + water

Question 11

acid + metal carbonate

Answer 11

salt + water + carbon dioxide

Question 12

apparatus for titration

Answer 12

*Beaker
*Burette
*Volumetric Pipette
*Conical Flask
*Volumetric Flask

Question 13

how to make a standard solution

Answer 13

1. weigh out precise amount of solid
2. add to small amount of water and dissolve the solid with a glass rod
3. transfer to a conical flask
4. rinse the beaker with distilled water
5. make up to the scratch mark with more water and add stopper

Question 14

how to work out conc of a standard solution:

Answer 14

concentration of a solution is the amount of solute dissolved in a solvent to make 1 dm3 of solution

Question 15

oxidation number of an ion

Answer 15

same as its charge

Question 16

oxidation number of hydrogen

Answer 16

+1 except in metal hydrides (NaH) when its -1

Question 17

oxidation number of oxygen

Answer 17

-2 except when in peroxides (H2O2) or bonded to fluorine

Question 18

oxidation number of fluorine

Answer 18

-1

Question 19

oxidation number of chlorine

Answer 19

-1 except when its bonded to oxygen or fluorine

Question 20

oxidation number of group 1 + 2

Answer 20

1+, 2+

Question 21

disproportionation reaction

Answer 21

reaction where the same element is both reduced and oxidised

Question 22

what happens to the reducing agent

Answer 22

it has been oxidised

Question 23

what happens to the oxidising agent

Answer 23

it has been reduced

Question 24

orbitals in each subshell:

Answer 24

s = 1
p = 3
d = 5
f = 7

Question 25

shape of s orbitals

Answer 25

sphere

Question 26

shape of p orbitals

Answer 26

dumbell