Formulae Equations and Amounts of Substance

Question 1

What is the symbol for amount of substance

Answer 1

n

Question 2

What is the unit used to measure amount of substance

Answer 2

mole

Question 3

What does the Avogadro constant represent

Answer 3

The number of atoms per mole of the carbon-12 isotope

Question 4

How to calculate the mass of 1 mole of the element?

Answer 4

Mass of 1 mole = relative atomic mass in grams

Question 5

How to calculate moles when
mass and molar mass are
given

Answer 5

Mr Mass Moles

Question 6

What is an empirical formula

Answer 6

Simplest whole number ratio of atoms of
each element present in a compound

Question 7

How to calculate empirical
formula?

Answer 7

mass/mr
Divides by the smallest
● If there is a decimal, divide by a suitable number
to make it into a whole number

Question 8

State Avogadro’s law

Answer 8

Under the same temperature and
pressure, one mole of any gas would
occupy the same volume

Question 9

How much volume does a gas
occupy, at room temperature
and pressure?

Answer 9

24 dm 3 or 24000 cm 3

Question 10

How do you convert from dm3 to cm3

Answer 10

1dm3 = 10000m3

Question 11

Define molar gas volume

Answer 11

The volume per mole of gas molecule

Question 12

Why do different gas particles occupy the same volume

Answer 12

The gas particles are very spread out, hence individual differences has no effect.

Question 13

How to calculate moles when gas volume is given

Answer 13

Volume (dm3) /24

Question 14

What are the ideal ways in which gases behave?

Answer 14

They are in continuous motion
● No intermolecular forces experienced
● Exert pressure when they collide with each other or
container
● No kinetic energy is lost in the collisions
● When temperature increases, kinetic energy of gases also
increase

Question 15

Unit of Pressure?

Answer 15

Pascal (Pa)

Question 16

Volume

Answer 16

m3 is standard

Question 17

gas constant?

Answer 17

8.314 mol-1

Question 18

0 celsius = waht kelvin

Answer 18

273K

Question 19

1 atm in Pa?

Answer 19

101325 Pa

Question 20

What does concentration of a solution mean

Answer 20

he amount of solute dissolved in 1 dm 3 of solvent

Question 21

What is the formulae for concentration

Answer 21

vol mol conc

Question 22

What is a standard solution

Answer 22

A solution of known concentration

Question 23

Steps to prepare a standard solution?

Answer 23

1. Weigh the solute using the weigh by difference method
2. In a beaker dissolve the solute using the solvent
3. Pour the solution into a volumetric flask
4. Rinse the beaker using the solution and add it to the flask
5. Add solvent to the flask carefully until it reaches the graduation line
6. Mix the solution thoroughly to ensure complete mixing

Question 24

What does the term concentrated mean

Answer 24

Large amount of solute per dm 3 of solvent

Question 25

What does the term dilute mean

Answer 25

Small amount of solute per dm 3 of solvent

Question 26

What is a species in a chemical reaction

Answer 26

Any particle that takes part in a reaction

Question 27

What are the 4 common state symbols?

Answer 27

Solid (s) Liquid (l) Gaseous (g) Aqueous (aq)

Question 28

What does the percentage yield mean

Answer 28

The efficiency of which reactants are converted into products

Question 29

What are the reasons for not obtaining 100% yield? (5)

Answer 29

● Reaction may be at equilibrium ● The reactants may be impure ● Side reactions could happen ● Reactants or products may be left behind while transferring ● Loss of products during separation and purification

Question 30

How is percentage yield calculated

Answer 30

Actual/theoretical x100

Question 31

What does atom economy tell us

Answer 31

The proportion of desired products compared with all the products formed in the reaction

Question 32

How is atom economy calculated

Answer 32

Desired/total x100

Question 33

Which type of reaction has 100% atom economy?

Answer 33

Addition reactions (two or more reactants are combined to form a product)

Question 34

What does systematic error mean

Answer 34

The same error appears in each measurement

Question 35

The error of mass measurement can be reduced by using which method

Answer 35

Weighing by difference method

Question 36

Explain how to measure using the weighing by difference method

Answer 36

Measure the mass of the container 2. Add the chemical to the container and weigh the container 3. Calculate the mass of the chemical 4. Transfer the chemical and remeasure the empty container 5. Calculate the mass of the chemical transferred

Question 37

Is the percentage error higher or lower, when the quantity measured has been reduced

Answer 37

Higher

Question 38

What is formula for %uncertainty

Answer 38

(precision error of equipment/value measured) x 100

Question 39

How do you find the limting reactant

Answer 39

Find moles from balanced equation See which is limiting from the ratio use no. moles of limiting to find out the mass that coulve been made