Topic 3

Question 1

What is the Law of conservation of mass ?

Answer 1

No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants

Question 2

In a chemical react what are the starting materials known as ?

Answer 2

Reactants

Question 3

In a chemical react what is the name of the chemicals formed ?

Answer 3

Products

Question 4

What ions do metals form

Answer 4

Positive ions

Question 5

What ions do non-metals form

Answer 5

Negative ions

Question 6

What is the relative atomic mass ?

Answer 6

The relative atomic mass of an element is the average mass of the isotopes of that element weighted to take into account the abundance of each isotope

Question 7

What is the relative formula mass ?

Answer 7

The relative formula mass of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the formula

Question 8

Important things about relative formula mass

Answer 8

• Relative formula mass has no units
• relative formula mass never involves big numbers

Question 9

How to calculate the percentage by mass of an element in a compound ?

Answer 9

Percentage by mass of an element = total relative atomic mass of the atoms of that element/relative formula mass of compound
x100

Question 10

What is Avogadros constant

Answer 10

6.02 x 10^23

Question 11

How to calculate the number of moles of an element ?

Answer 11

Mass (g) / relative atomic mass

Question 12

How to calculate the number of moles of a compound ?

Answer 12

Mass(g)/ relative formula mass