Atoms, Molecules And Stoichiometry

Question 1

Define unified atomic mass unit

Answer 1

One twelfth of the mass of carbon-12 atom.

Question 2

How much mass is in 1 unified atomic mass unit (1u or 1Da)

Answer 2

1.66 x 10–²⁷ kg

Question 3

Define relative atomic mass

Answer 3

Relative atomic mass (Ar) is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12.

Question 4

Define relative isotopic mass

Answer 4

Relative Isotopic mass is the mass of one isotope compared to one twelfth of the mass of one atom of carbon-12.

Question 5

Define Relative molecular mass

Answer 5

Relative molecular mass (Mr) is the weighted average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12.

Question 6

Define relative formula mass

Answer 6

Relative formula mass (Mr) is the weighted average mass of the formula unit compared to one twelfth of the mass of one atom of carbon-12.

Question 7

Formula unit

Answer 7

The simplest formula for a covalent giant structure or an ionic giant structure.

Question 8

Formula to find number of carbon in an organic compound.

Answer 8

(100 x abundance of [M+1]+ ion)
÷ (1.1 x abundance of M+ ion)

Question 9

Define mole.

Answer 9

A mole is the amount of substance which contains 6.02 × 10²³ specified particles. The particles can be atoms, molecules, ions or electrons.

Question 10

Common compound ions and metal ions:
Nitrate
Carbonate
Sulfate
Hydroxide
Ammonium
Zinc(ll)
Silver
Hydrogen carbonate
Phosphate

Answer 10

NO3(–)
CO3(2–)
SO4(2–)
OH(–)
NH4(+)
Zn(2+)
Ag(+)
HCO3(–)
PO4(3–)