Amount of Substance

Question 1

Define relative atomic mass, Ar.

Answer 1

Average mass of on element of an atom / 1/12 mass of carbon-12

Question 2

Define relative molecular mass, Mr.

Answer 2

Average mass of one molecule / 1/12 mass of carbon-12

Question 3

How do you find relative molecular mass?

Answer 3

Add up all of the relative atomic masses.

Question 4

What is Mr when referring to ionic compounds?

Answer 4

Relative formula mass.

Question 5

What is a mole?

Answer 5

6.022 x 10^23 particles

Question 6

Why is the Avagadro’s constant this number?

Answer 6

Number of atoms in 12g of carbon-12.

Question 7

What is the molar mass?

Answer 7

Mass per mole of unit substance.

Question 8

The relative atomic mass of any element in grams contains how many atoms?

Answer 8

1 mole.

Question 9

number of moles = ?

Answer 9

Mass / Mr

Question 10

What does a solution consist of?

Answer 10

A solvent with a solute dissolved in it.

Question 11

What does the concentration of a solution tell us?

Answer 11

How much solute is present in a known volume of solution.

Question 12

What is the equation for concentration in moldm^-3?

Answer 12

Number of moles / volume (dm^3)

Question 13

How do you convert from cm^3 to dm^3?

Answer 13

x10-3

Question 14

What is the ideal gas equation?

Answer 14

PV = nRT

Question 15

What is P and what is it measured in?

Answer 15

Pressure, Pa.

Question 16

What is V and what is it measured in?

Answer 16

Volume, m^3.

Question 17

What is n and what is it measured in?

Answer 17

Number of moles, moles.

Question 18

What is R and what is it and what is it measured in?

Answer 18

The ideal gas constant, 8.31 JK^-1mol^-1.

Question 19

The same number of moles of any gas has the same what under the same pressure and temperature?

Answer 19

Volume.

Question 20

Define empirical formula.

Answer 20

The formula that represents the simplest whole number ratio of the atoms of each element preset in the compound.

Question 21

Give an example of an empirical formula.

Answer 21

CO2.

Question 22

What is the first step in finding the empirical formula?

Answer 22

Find the masses of each element present in the compound.

Question 23

What is the second step in finding the empirical formula of a compound?

Answer 23

Find moles, moles = mass/Mr.

Question 24

What is the last step in finding the empirical formula of a compound?

Answer 24

Divide every value by the smallest number, use this as ratio.

Question 25

What is the molecular formula?

Answer 25

The formula that gives the actual number of molecules in a compound.

Question 26

How do you find the number of units of the empirical formula in the molecular formula?

Answer 26

Divide the relative molecular mass by the relative mass of the empirical formula.

Question 27

What is a spectator ion?

Answer 27

They don’t take part in the reaction.

Question 28

What is the equation for percentage atom economy?

Answer 28

(mass of desired product / total mass of reactants) x 100

Question 29

What does the atom economy tell us?

Answer 29

How many atoms in a reaction must be wasted in theory.

Question 30

What does the yield tell us?

Answer 30

How much is lost, the practical efficiency.

Question 31

What are conditions that cause loss?

Answer 31

Impure reactants, reversible reactions, side reactions, incomplete reactions, practical losses.

Question 32

Equation for yield?

Answer 32

(Grams of product obtained / theoretical max) x 100