2.1.4 Acids

Question 1

What is the formula of lab acids?

Answer 1

HCl
H2SO4
HNO3

Question 2

What are the formula of weaker acids?

Answer 2

Vinegar - CH3COOH
Methanoic acid - HCOOH

Question 3

What is the difference between strong and weak acids?

Answer 3

Strong acids = ion fully dissociates and fully ions (splits into ions)
Weak acids = partially dissociates into its acid
Weak acids and alkalis have a reversible dissociation

Question 4

What is an acid?

Answer 4

A source of hydrogen ions (H+)
In water give a pH of less than 7 can neutralise bases and alkali, hydrogen ion donors

Question 5

What is the difference between concentrated and dilute acids?

Answer 5

Concentrated - more acid (H+) ions in a given volume
Dilute - less acid (H+) ions in a given volume

Question 6

What is the active ingredient in acids?

Answer 6

• hydrogen
• H+ ions
• a proton donor

Question 7

Why is a H+ ion described as a proton?

Answer 7

When H becomes an ion, it loses its last electron and only the proton is left

Question 8

What is a base?

Answer 8

A proton acceptor

Question 9

What is the difference between a base and an alkali?

Answer 9

An alkali is a soluble base that releases OH- ions in aqueous solution

Question 10

What are common bases?

Answer 10

MgO
NaOH
CuO
Ca(OH)2

Question 11

What is the general neutralisation reaction?

Answer 11

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

Question 12

What is an alkali?

Answer 12

Soluble in water to form solutions
Source of OH- ions and proton acceptors
A substance that gives a pH over 7 (in water)
Release OH- ions when dissolve in solution

Question 13

What is the formula of 2 common strong alkalis?

Answer 13

NaOH
KOH

Question 14

Why is ammonia a weak alkali?

Answer 14

NH3 dissolves in water to form a weak alkaline solution

Question 15

What is an amphoteric substance?

Answer 15

• can behave as an acid or a base
• amino acid molecule e.g. glycine contains
• COOH to donate protein
• NH2 to accept proton

Question 16

What are the general equations for salt formation?

Answer 16

Acid + alkali -> metal salt + water
Acid + base -> metal salt + water
Acid + carbonate -> metal salt + water + carbon dioxide
Acid + metal -> metal salt + hydrogen

Question 17

Examples of bases

Answer 17

Metal oxides or hydroxides

Question 18

How to make a standard solution?

Answer 18

• dissolve solid in beaker using distilled water, stirring until fully dissolved
• pour into volumetric flask using funnel
• rinse beaker and glass rod with water
• rinse funnel
• fill until line is level with bottom of meniscus when at eye level
• add stopper and invert several times to mix particles throughly

Question 19

Titration method

Answer 19

• fill biurette with acid
• use pipette to add alkali (standard solution) to conical flask
• add indicator
• titrate and record start and finish volume
• repeat until concordant results obtained (0.1cm3)