quantitative chemistry

Question 1

What is the conservation of mass?

Answer 1

No atoms are lost or made during a chemical reaction, so the mass of products = reactants.

Question 2

What is the measurement of moles?

Answer 2

moles:

• chemical amounts are measured in moles
• the mass of one mol is numerically equal to it’s relative atomic mass
• one mol of a substance contains the same number of atoms/molecules as one mole of another substance

Question 3

What is Avogadro’s constant?

Answer 3

Avogadro’s constant gives the amount of atoms, ions or molecules in one mol of a substance.
6.02 x 10^23

Question 4

How do you calculate moles?

Answer 4

moles = mass / relative atomic mass

Question 5

What is the limiting reactant?

Answer 5

The limiting reactant is the reactant that is not used in excess. It limits the amount of product formed.

Question 6

What is concentration?

Answer 6

Concentration shows the mass or moles of a solute in a given volume of solution.

Question 7

How many dm^3 is in 1000cm^3?

Answer 7

1000cm^3 = 1dm^3

Question 8

What are the two ways to calculate concentration?

Answer 8

concentration = mass / volume
concentration= moles / volume

Question 9

What is the percentage yield?

Answer 9

Percentage yield is how much of the expected product you actually obtain.

Question 10

How do you calculate percentage yield?

Answer 10

percentage yield = (mass of obtained product / expected mass of product) x 100

Question 11

Why is the percentage yield not always 100%?

Answer 11

percentage yield isn’t always 100% as:

• some of the product may be lost when separated from reaction mixture
• some of the reactants may react in different ways to the expected reaction
• may be incomplete as it is reversible

Question 12

What is the atom economy?

Answer 12

Atom economy is a measure of the amount of starting reactants that have ended up as useful products. By minimising the production of unwanted products, we save money.

Question 13

How do you calculate atom economy?

Answer 13

atom economy = (atomic mass of desired products / atomic mass of all products) x 100

Question 14

How do you calculate the volume of a gas?

Answer 14

volume of gas (dm^3) = moles x 24

Question 15

Fill in the blanks:

__ mol of any gas occupies a volume of _____ at __ degrees Celcius and __ atmospheric pressure.

Answer 15

One mol of any gas occupies a volume of 24dm^3 at 20 degrees Celcius and 1 atmospheric pressure.

Question 16

How do you convert mol/dm^3 to g/dm^3?

Answer 16

To convert mol/dm^3 to g/dm^3, you multiply it by the relative formula mass.