Acids, Bases and Salts

Question 1

what colour is produced by litmus paper when in acidic solution?

Answer 1

red

Question 2

what colour is methyl orange in alkali?

Answer 2

yellow

Question 3

what colour is phenolphthalein in acid?

Answer 3

colourless

Question 4

what colour is methyl orange in acid?

Answer 4

red

Question 5

what colour is litmus paper in alkali?

Answer 5

blue

Question 6

what colour is phenolphthalein in alkaline?

Answer 6

pink

Question 7

what colour is a universal indicator in acid?

Answer 7

red

Question 8

what colour is universal indicator in alkaline?

Answer 8

blue

Question 9

what is the word equation for metals reacting with acid?

Answer 9

metal + acid ⇒ salt + hydrogen

Question 10

what is the word equation for acids reacting with bases?

Answer 10

acid + base ⇒ salt + water

Question 11

what does hydrochloric acid form?

Answer 11

chloride

Question 12

what does nitric acid form?

Answer 12

nitrate

Question 13

what does sulphuric acid form?

Answer 13

sulphate

Question 14

what is the word equation for acid reacting with metal oxide?

Answer 14

acid + metal oxide ⇒ salt + water

Question 15

what is the word equation for acid and metal hydroxide reacting together?

Answer 15

acid + metal hydroxide ⇒ salt + water

Question 16

what is the word equation for acid reacting with metal carbonate?

Answer 16

acid + metal carbonate ⇒ salt + water + carbon dioxide

Question 17

describe how to prepare salts from neutralisation reactions ( i.e. dilute acid reacting with excess metal oxide or metal carbonate)

It can also be seen in terms of H⁺ and OH^-

Answer 17

acid + base => salt + water

H⁺ (aq) + OH^-(aq) => H₂O (l)

Question 18

explain how to carry out an acid-alkali titration

Answer 18

Method

• Use the pipette and pipette filler to add 25 cm³ of alkali to a clean conical flask.
• Add a few drops of an indicator and put the conical flask on a white tile (so you can see the colour of the indicator more easily).
• Fill the burette with acid and note the starting volume.
• Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
• Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading.
• Repeat steps 1 to 5 until you get consistent readings
• The same method works for adding an alkali to an acid - just swap around the liquids that go into the conical flask and burette.

Question 19

what is an acid?

Answer 19

a substance that produces hydrogen ions ( H+) when dissolved in water

Question 20

what is a base?

Answer 20

bases are substances that react with acids and neutralises them

Question 21

explain the term weak and strong, as applied to acids

Answer 21

Strong acids

In aqueous solution, a strong acid is one that completely dissociates (splits up) into ions.

Example: hydrochloric acid.

HCl(g) + H2O(l)→H+(aq) + Cl-(aq)

This is not a reversible reaction, and 100% of the HCl molecules dissociate into ions.

Other strong acids include nitric acid and sulphuric acid.

Weak acids

In aqueous solution, a weak acid is one that only partially dissociates into ions. As a result, a state of equilibrium is produced.

Question 22

explain the term weak and strong, as applied to bases

Answer 22

Strong bases

In aqueous solution, a strong base is one that completely ionises.

Example: sodium hydroxide.

NaOH(s) + H2O(l)→Na+(aq) + OH-(aq)

This is not a reversible reaction, and 100% of the NaOH(s) splits into free ions.

Weak bases

In aqueous solution, a weak base is one that only partially ionises. Just as with weak acids, a state of equilibrium is produced.

Question 23

hydrochloric acid + sodium carbonate => sodium chloride + water + carbon dioxide (add metal carbonates to give salt + water + carbon dioxide)

Answer 23

2HCl + Na₂CO₃ => 2NaCl + H₂O + CO₂

Question 24

sulfuric acid + calcium carbonate => calcium sulfate + water + carbon dioxide

Answer 24

H₂SO₄ + CaCO₃ => CaSO₄ + H₂O + CO₂

Question 25

nitric acid + calcium carbonate => calcium nitrate + water + carbon dioxide

Answer 25

2HNO₃ + CaCO₃ => Ca(NO₃)₂ + H₂O + CO₂

Question 26

hydrochloric acid + copper oxide => copper chloride + water (acids react with metal oxide to form salt + water)

Answer 26

2HCl + CuO => CuCl₂ + H₂O

Question 27

sulfuric acid + zinc oxide => zinc sulfate + water

Answer 27

H₂SO₄ + ZnO => ZnSO₄ + H₂O

Question 28

nitric acid + copper oxide => copper nitrate + water

Answer 28

2HNO₃ + CuO => Cu(NO₃)₂ + H₂O

Question 29

what salts are soluble in water?

Answer 29

potassium, sodium & ammonium (soluble carbonates), nitrates, most chlorides (except silver chloride), most sulfates (except barium and calcium sulfate)

Question 30

what does the rate of reaction depend on?

Answer 30

temperature, concentration (or pressure for gases), catalyst & size of particles (or surface area)

Question 31

how do you find the rate of reaction?

Answer 31

rate of reaction = amount of reactant used or amount of product formed / time