Acids, Bases and Salts

Question 1

What are colours of indicators in acidic solution?

Answer 1

Red litmus - red
Blue litmus - red
Methyl orange - red
Phenolphthalein - colourless

Question 2

What are the colours of indicators in neutral solution?

Answer 2

Red litmus - red
Blue litmus - blue
Methyl orange - orange
Phenolphthalein - colourless

Question 3

What are the colours of indicators in alkaline solution?

Answer 3

Red litmus - blue
Blue litmus - blue
Methyl orange - yellow
Phenolphthalein - pink

Question 4

What pH is a strong acid?

Answer 4

pH 0-2
E.g. gastric juice.

Question 5

What pH is a weak acid?

Answer 5

pH 3-6
E.g. vinegar.

Question 6

What pH is a neutral solution?

Answer 6

pH 7
E.g. pure water

Question 7

What pH is a weak alkali?

Answer 7

pH 8-11
E.g. blood

Question 8

What pH is a strong alkali?

Answer 8

pH 12-14
E.g. washing soda solution

Question 9

What happens when acids dissolve in water?

Answer 9

Produce hydrogen ions.

Question 10

What happens when alkalis dissolve in water?

Answer 10

Produce hydroxide ions.

Question 11

What is the equation for neutralisation?

Answer 11

H+(aq) + OH-(aq) > H2O(L)

Question 12

How do you investigate temp change during neutralisation reaction?

Answer 12

Record temp of acid.
Stir gently alkali with acid.
Record temp after.
Take temps away from each other to find temp change.

Question 13

What is the chemical test for hydrogen?

Answer 13

Lighted splint placed in test tube of hydrogen gas there is squeaky pop.

2H2 + O2 > 2H2O

Question 14

What is the chemical test for carbon dioxide?

Answer 14

Bubbled through limewater, limewater changes from colourless clear solution to cloudy or milky suspension.

Ca(OH)2h(aq) + CO2(g) > CaCO3(s) + H2O(L)

Question 15

What is the chemical test for oxygen?

Answer 15

Glowing splint placed in test tube of oxygen it delights.

Question 16

What are the colours of different copper salts?

Answer 16

Copper(II) oxide, CuO - black
Copper(II) carbonate, CuCO3 - green
Copper(II) sulfate (anhydrous), CuSO4 - white
Copper(II) sulfate (hydrated), CuSO4.5H2O - blue
Copper(II) chloride, CuCl2(aq) - blue-green

Question 17

Why are hazard symbols used?

Answer 17

Eye catching.
Understood by those who cannot read.
Internationally recognised symbols.
Easily recognised symbols indicating warning.

Question 18

What does explosive sign mean?

Answer 18

May explode when heated, exposed to flame or knocked.

Question 19

What does toxic sign mean?

Answer 19

Serious risk of causing death by poisoning when swallowed or breathed.

Question 20

What does caution sign mean?

Answer 20

Less poisonous than toxic substances, but must be handled with care. May irritate skin or eyes.

Question 21

What does corrosive sign mean?

Answer 21

Destroy flesh and other materials.

Question 22

What does highly flammable sign mean?

Answer 22

Easily catch fire.

Question 23

What are strong acids?

Answer 23

Completely ionised in water - break up completely into ions and high concentration hydrogen ions in solution.

Question 24

What are weak acids?

Answer 24

Partially ionised in water and small amount of molecules break into ions added to water.

Question 25

What is a concentrated acid?

Answer 25

Contains large amount of acid particles dissolved per unit volume.

Question 26

What is a dilute acid?

Answer 26

Contains small amount of acid dissolved per unit volume.

Question 27

How is a salt prepared?

Answer 27

1. Add solid base in excess to beaker of acid and stir with glass rod until solid dissolved in acid.
2. Pass solution through filter paper, separate insoluble residue from filtrate solution, passes into conical flask.
3. Evaporate off half of volume of solution over Bunsen burner and allow aqueous solution to cool and form.
4. Pass salt crystals through filter paper to get fry hydrated salt crystals and let form into solid salt.