write the molecular formula for each of the following compounds :
1. sulphur trioxide
2.Iron (lll) suphide
3. Ammonia
Find the number and names of elements present in them and calculate their molecular masses
Answers
Answer:
1. Sulphur trioxide
A molecule of sulphur trioxide is represented by the formula SO3.
The elements present in it are sulphur dioxide and oxygen.
One molecule of sulphur trioxide has one atom of sulphur and three atoms of oxygen.
Molecular mass of sulphur trioxide (SO3)
= 32 + 3 x 16
= 32 + 48 = 80 amu.
2. Iron (II) sulphide
A molecule of iron (II) sulphide is represented by the formula FeS.
The elements present in it are iron and sulphur.
One molecule of iron (II) sulphide has one atom of iron and one atom of sulphur.
Molecular mass of iron (II) sulphide (FeS)
= 55.5 + 32
= 87.5 amu.
3. Ammonia
A molecule of ammonia is represented by the formula NH3.
The elements present in it are nitrogen and hydrogen.
One molecule of ammonia has one atom of nitrogen and three atoms of hydrogen.
Molecular mass of ammonia (NH3)
= 14 + 3 x 1
= 14 + 3
= 17 amu.