C3.3 - Types Of Chemical Reactions

Question 1

What is a redox reaction?

Answer 1

A redox reaction is a reaction in which reduction and oxidation happen at the same time

Question 2

What is reduction and oxidation?

Answer 2

• Reduction is the loss of oxygen from a substance.
• Oxidation is the gain of oxygen by a substance.
• Reduction is the gain of electrons from a
  substance.
• Oxidation is the loss of electrons from a substance.

Question 3

What is an oxidising agent?

Answer 3

A substance that oxidises another substance by donating oxygen or by accepting electrons.

Question 4

What is a reducing agent?

Answer 4

A substance that reduces another substances by accepting oxygen or by donating electrons.

Question 5

What do half equations show?

Answer 5

A half equation shows the change that happens to one reactant in a reaction.

Question 6

What is an acid?

Answer 6

An acid is a substance that releases H+(aq), hydrogen ions, when it is dissolves in water to make an aqueous solution.

Question 7

What is a base?

Answer 7

A substance that can neutralise acids.

Question 8

What is an alkali?

Answer 8

• An alkali is a base that can dissolve in water.
• Releases hydroxide ions, OH- (aq), when it
  dissolves in water.

Question 9

What does the pH of a solution show?

Answer 9

- The pH of a solution describes its relative acidity 
  or alkalinity.
- pH < 7 means acidic.
- pH = 7 means neutral.
- pH > 7 means alkaline.

Question 10

How do you measure pH with a pH meter?

Answer 10

• First need to calibrate the pH meter to get
  accurate measurements.
• Wash the pH probe with water, then put it into a
  calibration buffer.
• Adjust the reading to match the pH of the buffer
  solution.
• Wash the probe with water then put it into the
  solution and record the reading on the metal.
• Make sure to wash the probe between each
  measurement to make sure that the probe is not
  contaminated with the previous sample as this
  would affect the reading.

Question 11

What is a neutralisation reaction?

Answer 11

Neutralisation is the reaction between an acid and a base to form a salt and water.

Question 12

How do you predict the salt produced in a neutralisation reaction?

Answer 12

• The first part comes from the metal in the base
  or alkali.
• The second part of the name comes from the
  acid used.

Question 13

What ionic equation models neutralisation in solution?

Answer 13

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

Question 14

Give the formula when acids react with carbonates.

Answer 14

acid + metal carbonate -> Salt + Water + Carbon dioxide (gas - released as bubbles in the reaction)

Question 15

Why does a lump of calcium carbonate appear to dissolve in water even though its insoluble in water?

Answer 15

The salt formed is aqueous and the carbon dioxide is released as bubbles which is why a lump of insoluble calcium carbonate appears to dissolve if you add acid to it.

Question 16

What is the term that chemists use to describe bubbling or fizzing?

Answer 16

Effervescence

Question 17

Give the word equation when an acids reacts with a metal?

Answer 17

Acid + Metal -> Salt + Hydrogen (gas - released as bubbles)

Question 18

If magnesium is insoluble why does a piece of magnesium ribbon appear to dissolve if you put it into acid?

Answer 18

Soluble magnesium salt is formed and the hydrogen gas is released as bubbles which makes the magnesium appear to dissolve.

Question 19

What is the difference between a dilute acid and concentrated acid?

Answer 19

A dilute acid contains a low ratio of acid to volume of solution whereas a concentrated acid contains a high ratio of acid to volume of solution.

Question 20

What is the difference between weak and strong acids?

Answer 20

• Weak acids partially ionise which means only a
  small fraction of their molecules release H+ ions
  when dissolved in water.
• Strong acids fully ionise which means all their
  molecules H+ ions when dissolved in water.
• Weak acids use that double arrow symbol to
  show the hydrogen ion and negatively charged
  ion reaction not going fully to completion.

Question 21

What happen as the concentration H+ ions increases by a factor in 10 in an aqueous solution?

Answer 21

The pH of the solution decreases by 1.

Question 22

What does a pH titration curve show?

Answer 22

A pH titration curve shows the effect on pH of changing the hydrogen ion concentration during a neutralisation reaction.