C4 - Chemical Calculations

Question 1

Equation for moles?

Answer 1

Moles = mass (g) / Mr

Question 2

How are the masses of atoms found?

Answer 2

By measuring them relative to carbon 12

Question 3

Balanced symbol equation tells you what?

Answer 3

The number of moles of substances in equations.

Question 4

What is a limiting reactant?

Answer 4

The one NOT in excess, which gets used up first.

Question 5

E. Moles of a gas?

Answer 5

Moles = volume / 24dm3

Question 6

What is Avogadro constant?

Answer 6

The number of particles contained in a mole. 6.02*10 to the 23

Question 7

Examples of strong acids? (3)

Answer 7

Hydrochloride acid, nitric acid and sulfuric acid.

Question 8

Examples of strong alkalis? (2)

Answer 8

Aqueous sodium hydroxide and aqueous potassium hydroxide

Question 9

Suitable indicators for titrations? (2)

Answer 9

Methyl orange and phenolphthalein

Question 10

When doing a titration, where does the
1) acid
2) alkali
Go?

Answer 10

Acid in the burette

Alkali in the conical flask (with indicator)

Question 11

What information must be known to fund the concentration of an acid/alkali from a titration?

Answer 11

The relative bylines of acid and alkali used

The conc. of other acid/alkali.

Question 12

E. Percentage yield?

Answer 12

Yield from reaction/maximum theoretical yield * 100%

Question 13

Why is atom economy important?

Answer 13

To minimise costs, sustainable development so less waste is produced.

Question 14

E. Atom economy?

Answer 14

Atom economy = relative formula mass of desired product / sun of the relative formula mass of all the products or reactants. *100%

Question 15

How can ethanol be produced?

Answer 15

Hydration and fermentation?

Question 16

How does hydration of ethanol work?

Answer 16

Ethene reacts with steam to form ethanol.

Question 17

How does fermentation of ethane work?

Answer 17

Glucose is fermented.

Question 18

Which way of production of ethanol has a higher atom economy?

Answer 18

Hydration.

Question 19

Factors to consider when choosing a reaction pathway? (6)

Answer 19

• atom economy
• cost of reactants
• percentage yield
• rate of reaction
• equilibrium position
• usefulness of the by-products.

Question 20

In electrolysis if aqueous solutions , what is produced at the anode?

Answer 20

Oxygen unless it contains halide ions. If halide ions are produced then the halogen is given off.

Question 21

In electrolysis if aqueous solutions , what is produced at the cathode?

Answer 21

Hydrogen if the metal is more reactive then hydrogen. The metal is produced if the metal is less reactive then hydrogen.

Question 22

Which metals can be extracted from their idea using electrolysis?

Answer 22

Metals more reactive then carbon.

Question 23

What is a 1 on the ph scale?

Answer 23

Very Acidic

Question 24

What is 7 on the pH scale?

Answer 24

Neutral

Question 25

What is 14 on the pH scale?

Answer 25

Very alkaline.

Question 26

What ions do acids contain?

Answer 26

Hydrogen ions, H+ (aq)

Question 27

What ions do alkalis contain?

Answer 27

Hydroxide ions, OH- (aq)

Question 28

What happens when a strong acid reacts with water?

Answer 28

It is completely ionised.

Question 29

What is the pH a measure of?

Answer 29

The concentration of H+ ions in a solution.

Question 30

What does the pH decrease of 1 indicate?

Answer 30

The concentration of H+ ions has increased by factor 10.

Question 31

A stronger acid will have a higher concentration of…..

Answer 31

Hydrogen ions.