C4: Chemical calculations

Question 1

What is a mole?

Answer 1

amount of substance

Question 2

What is Avogadro’s number?

Answer 2

6.02 x 10 to the power of 23

Question 3

How do you work out the amount of moles?

Answer 3

mass / Mr

Question 4

What is the units for Moles?

Answer 4

mol

Question 5

How do you work out the amount amount of atoms or molecules?

Answer 5

mol x avagadro

Question 6

What is another word for the balancing numbers?

Answer 6

stochiometry

Question 7

Why might chemical reactions not be completely successful?

Answer 7

because of the equipment.
you could lose products and reactants whilst transferring.
they could lose gases to the atmosphere.
the reaction may not be complete.

Question 8

What is the limiting reactant?

Answer 8

the reactant that gets used up first.

Question 9

what is the yield?

Answer 9

the mass of a product

Question 10

How do you work out the percentage yield?

Answer 10

actual mass of product/ theoretical mass of product x 100

Question 11

What are the steps to calculating reacting masses?

Answer 11

1. Balance the equation.
2. Work out the moles of the ‘known’ substance.
3. Work out the moles of the unknown substance.
4. Answer the question.

Question 12

What is concentration?

Answer 12

the amount of a substance in a volume.

Question 13

what is 1dm cubed in cm cubed?

Answer 13

1000 cm cubed

Question 14

what is the equation for concentration?

Answer 14

c=n/v

Question 15

What are the units for concentration?

Answer 15

mol/dm cubed