Amount of a substance

Question 1

What is relative atomic mass

Answer 1

Average was of one atom of an element divided by 1/12 mass of 1 atom of C12

Question 2

What is relative molecular mass

Answer 2

average mass of one molecule divided by 1/12 of one atom of C12

Question 3

What is relative formula mass

Answer 3

Same as relative molecular mass but used of ionic compounds

Question 4

What does Avogadro’s constant represent?

Answer 4

The number of particles in a mole

Question 5

What is concentration of a substance measured in

Answer 5

mol dm-3

Question 6

What is the formula for the number of moles?

Answer 6

Mass/Mass of 1 mole

Question 7

What is the equation linking volume, conc., and moles

Answer 7

moles = vol * conc

Question 8

What is the ideal gas equation

Answer 8

PV=NRT
Pressure in Pa
Volume in m3
Temp in kelvin

Question 9

How do you calculate the empirical formula

Answer 9

Find masses (g) of each of the elements present in a compound

Find n.o of moles using Mr and masses

Convert number of moles of each element in a whole number ratio

Question 10

How do you calculate empirical formula from RMM and Percentages

Answer 10

Find percent of each atom in molecule
*
Then divide each answer by the atomic number of the element
*
Divide down to get smallest whole number ratio

Question 11

What is atom economy

Answer 11

Works out the theoretical mass of product

Question 12

How do you calculate atom economy?

Answer 12

% atom economy =( molecular mass of desired product / Sum of molecular masses of all reactants ) x 100

Question 13

What is the percentage yield of a chemical reaction

Answer 13

How efficient the process is and how much loss there is

Question 14

What is relative isotopic mass

Answer 14

The average mass of an isotope compared to 1/12 the mass of a Carbon 12 atom

Question 15

What is empirical formula

Answer 15

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

Question 16

What is molecular formula?

Answer 16

The actual number of atoms of each element in a compound

Question 17

Why is it important to have reactions with high atom economy

Answer 17

*Cheaper as less by products
*Waste chemicals can be harmful to environment

Question 18

Why don’t actual and theoretical yield match up

Answer 18

Chemicals lost on apparatus
May be gaseous and lost to environment

Question 19

What is the formula for number of particles

Answer 19

Avogadro’s constant x Number of moles

Question 20

How does rinsing a burette with distilled water affect titre value

Answer 20

Titre value increases as Burette is more dilute