C3 - Quantitative Chemistry

Question 1

mass = 2

Answer 1

moles X mr
concentration X volume

Question 2

moles = 3

Answer 2

mass / mr
concentration X volume
volume / 24

Question 3

relative formula mass = 1

Answer 3

mass / moles

Question 4

concentration = 1

Answer 4

mass or moles / volume

Question 5

volume = 2

Answer 5

mass or moles / concentration
moles X 24

Question 6

24 = 1

Answer 6

volume / moles

Question 7

percentage mass =

Answer 7

number of atoms of element X Ar / mr X 100%

Question 8

percentage yield =

Answer 8

actual yield / predicted yield X 100%

Question 9

atom economy =

Answer 9

mr of desired product / sum of mr of reactants X 100%

Question 10

How do you get from cm3 to dm3?

Answer 10

divide by 1000

Question 11

How do you get from dm3 to cm3?

Answer 11

times by 1000

Question 12

Define relative formula mass (mr)

Answer 12

total mass of all the atoms in the molecule

Question 13

How do you calculate relative formula mass?

Answer 13

1) Expand any brackets
2) Find the atomic masses for the elements
3) Times the atomic masses by how many times the element appears in the formula
4) Add them together

Question 14

What does the law of conservation of mass mean?

Answer 14

mass of products = mass of reactants

Question 15

What does Ar mean?

Answer 15

relative atomic mass

Question 16

What is the value of 1 mole?

Answer 16

6.022 X 10 to the power of 23 molecules

Question 17

Why might the mass of a reaction vessel might decrease during a reaction?

Answer 17

gas may be released

Question 18

Give the 5 steps how to solve a limiting reactants question (calculate the mass of ______ formed when __g of ______ is used)

Answer 18

1) Circle the two substances mentioned in the question
2) Calculate the mr of both
3) Calculate the number of moles of the KNOWN mass (mass/mr)
4) Use the molar ratio (using the big numbers) to calculate how many moles of unknown substance
5) Calculate mass of UNKNOWN mass (moles X mr)

Question 19

Define excess reagent/reactant

Answer 19

Uses a larger amount than required to ensure a complete reaction

Question 20

Define limiting reagent/reactant

Answer 20

Limits the amount of product made

Question 21

Define concentration

Answer 21

Concentration is the number of particles in a given volume

Question 22

Why is the constant 24dm3 used when calculating volume of gases?

Answer 22

1 mole of any gas will occupy 24dm3

Question 23

Why is percentage yield not 100%?

Answer 23

-raw materials may not be pure
-some products may be left behind in apparatus
-reaction may not be completely finished

Question 24

Which is the only equation where you don’t ignore the big number when calculating mr?

Answer 24

Atom economy

Question 25

Define atom economy

Answer 25

a measure of the amount of starting materials that end up as useful products