Calculations in Chemistry - C4

Question 1

What is the definition of relative formula mass

Answer 1

It is the average mass of the compound with 1/12 the mass of a carbon 12 atom

Question 2

What is the definition of relative atomic mass

Answer 2

It is the mass of an atom to the mass of an atom of carbon 12

Question 3

What is a mole

Answer 3

A mole of atoms is 6.02 x10 23 atoms

This is avogadros number

Question 4

what is the equation for moles

Answer 4

moles = mass (g) / Mr

Question 5

What is percetage yield

Answer 5

It is how much product is made in a chemical reaction

Question 6

What is the theorectical yield of a reaction

Answer 6

It is the yield that would happen if the reaction was perfect

Question 7

What is the equation for percentage yield

Answer 7

= actual yield/theorectical yield x100

Question 8

What are the reasons for less than 100% yield

Answer 8

impure raw materials
incomplete reaction
competing reactions
Miss weighing
loss of product

Question 9

What is the equation for atom economy

Answer 9

= Formula mass of product/Total formula mass of reactants x100

Question 10

What is the atom economy of a reaction

Answer 10

It is the measure for how efficient the reaction is

Question 11

What volume does a mole of gas take up at room temperature

Answer 11

24 dm3 = 24,000 cm3

Question 12

What is the equation for moles of gas

Answer 12

= volume of gas (dm3) / 24

Question 13

what is the equation for relative atomic mass

Answer 13

(Percentage x relative atomic mass) / 100

Question 14

What is a titration

Answer 14

A method where a solution of a known concentration is used to determine the unknown concentration of a substance

Question 15

What is the equation for moles

Answer 15

moles = concentration x volume

Question 16

How does a titration work

Answer 16

Use the volume and concentration of one reactant to calculate the moles
Use the equation to find the moles of the other reactant
Calculate the volume or concentration as required of that reactant