General chemistry

Question 1

What is bond energy?

Answer 1

• The amount of energy required to break one mole of a particular covalant bond

Question 2

What type of battery are alkine batteries

Answer 2

• Non-rechargable

Question 3

How do fuel cells work?

Answer 3

• As fuel enters the cell, it becomes oxidised (loses an electron) which sets up a potential difference across the cell (as there is now a flow of electrons from the anode to the cathode)
• The ion of the fuel now moves across the electrolyte to the cathode where is reacts with the electrons it had previously lost and reactant at the cathode to form heat and a new molecule
• The most common is the hydrogen - oxygen fuel cell. Here, hydrogen is the fuel that becomes oxidised. It then reacts with oxygen at the cathode to form water and heat

Question 4

What is the relative atomic mass?

Answer 4

• The average mass of all isotopes of an element

Question 5

What is Avagadro’s constant?

Answer 5

• 6.02 x 10^23 particles (1 mole)

Question 6

How to calculate volume of gas?

Answer 6

• Mole x 24

Question 7

How to calculate concentration of a solution?

Answer 7

• C = M / V
• Mass / volume

Question 8

How to calculate atom economy of a reaction?

Answer 8

• (Mr of desired product / Mr of total product) x 100

Question 9

Why is it important to consider atom economy?

Answer 9

• Raw materials are expensive (reactions with low atom exonomy are less profitable)
• It is less sustainable to use large amounts of reactants to make small amounts of products
• Waste products are expensive to get rid off

Question 10

Why may our actual yield be less than our theoretical yield?

Answer 10

• The reactants might not all react (reversible reaction - reaction has reached equilibrium)
• There might be side reactions
• Some of the product might have been lost (gas might have escaped)