C3.3

Question 1

What is a redox reaction?

Answer 1

A reaction where a reduction and oxidation occurs at the same time

Question 2

What is a reduction?

Answer 2

Loss of oxygen from a substance or gain of electrons

Question 3

What is oxidation?

Answer 3

Gain of oxygen by a substance or loss of electrons

Question 4

What is reducing agent?

Answer 4

The compound that reduces the other (removes the oxygen from the substance to itself)

Question 5

What is the oxidising agent?

Answer 5

The compound that oxidised the other (it is getting reduced by oxidizing the other)

Question 6

What is an acid?

Answer 6

Substance that releases hydrogen ions when dissolving in water to make an aqueous solution

Question 7

What is a base?

Answer 7

Substance that neutralises acids
If a base can dissolve in water it is also an alkali

Question 8

What is an alkali?

Answer 8

Releases hydroxide ions when dissolving innwsyer to form an aqueous solution

Question 9

What is the pH of an acid?

Answer 9

pH < 7

Question 10

What is the pH of a neutral solution?

Answer 10

pH = 7

Question 11

What is the pH of an alkaline?

Answer 11

pH > 7

Question 12

What is neutralization?

Answer 12

Reaction between an acid, base or an alkali to form a salt and water only
Salt made depends on the acid and base used
ACID + BASE > SALT + WATER

Question 13

How does the pH change depending on what is added to what?

Answer 13

If a base/alkali is added to an acid the pH goes from less than 7 to greater than 7
If an acid is added to a base/alkali the pH goes from greater than 7 to less than 7

Question 14

How can you predict the salt made?

Answer 14

If you know the acid and base/alkali used
The salts have two parts:
- first part is from the metal in the base or alkali
- second part comes from the acid used

Question 15

What happens during neutralization in solution?

Answer 15

Acids contain hydrogen ions
Alkaline solutions contain hydroxide ions
These react together to produce water
H + OH > H2O

Question 16

What happens when acids react with carbonates?

Answer 16

ACID + CARBONATE > SALT + WATER + CARBON DIOXIDE
The carbon dioxide is released as bubbles in the acid during the reaction

Question 17

What is effervescence?

Answer 17

Bubbling or fizzing

Question 18

What happens when acids react with metals?

Answer 18

ACID + METAL > SALT + HYDROGEN
The hydrogen is released as bubbles in the acid

Question 19

What is a dilute and concentrated acid?

Answer 19

Dilute acid = low ratio of acid to volume of solution
Concentrated acid = contains a high ration of acid to volume

Question 20

What are weak and strong acids?

Answer 20

Weak = partially ionized (only a small fraction of the molecules release hydrogen ions in an aqueous solution)
Normally not completed reactions (reversable arrow)
Strong = fully ionized (all molecules release hydrogen ions)

Question 21

How is pH linked to hydrogen ion concentration?

Answer 21

In an aqueous solution as the concentration of H ions increases by a factor of 10 the pH decreases by 1

Question 22

What pH would a concentrated acid have?

Answer 22

Lower pH

Question 23

What pH would a strong acid have?

Answer 23

Lower pH

Question 24

What is a pH titration curve?

Answer 24

Shows the effect on pH of changing the hydrogen ion concentration during a neutralisation reaction

Question 25

How to do the experiment to draw a pH titration curve?

Answer 25

1) transfer 25cm^3 of dilute alkali to a beaker
2) estimate its pH using universal indicator solution and a colour chart or measure with a pH meter
3) add 1cm^3 of dilute acid, stir and record the pH
4) continue until you’ve added an excess of acid
5) plot a graph of pH against volume of acid added