EL 1 - Formulae, Equations and Amount of Substance

Question 1

What is mass number?

Answer 1

The total number of nucleons (protons and neutrons) present in the nucleus of an atom

Question 2

What is atomic number?

Answer 2

The number of protons present in the nucleus of an atom

Question 3

What is relative atomic mass?

Answer 3

Relative atomic mass is the mean weighted mass of an atom of an element compared with 1/12th the mass of an atom of carbon-12

Question 4

What is relative molecular mass?

Answer 4

Relative molecular mass is the mean weighted mass of a molecule compared with 1/12th the mass of an atom of carbon-12

Question 5

What is relative formula mass?

Answer 5

Relative atomic mass is the sum of the mean weighted masses of all atoms in the formula of a compound compared with 1/12th the mass of an atom of carbon-12

Question 6

What is relative isotopic mass?

Answer 6

Relative isotopic mass is the mass of an atom isotope compared with 1/12th the mass of an atom of carbon-12

Question 7

What is the mole?

Answer 7

A mole = the amount of substance containing as many particles as there are atoms in 12g of carbon-12
1 mole = 6.02 x 10^23 items = Avogadro’s constant

Question 8

What is an ionic equation?

Answer 8

An ionic equation is an equation in which only the non-spectating ions are shown

Question 9

How is percentage yield calculated?

Answer 9

percentage yield = (actual yield) / (expected yield) x 100

Question 10

How is percentage composition by mass calculated?

Answer 10

percentage composition = (mass of desired substance) / (mass of mixture) x 100

Question 11

How is a standard solution prepared from a concentrated solution?

Answer 11

1. A certain volume of the concentrated solution is added to a volumetric flask in order to get the desired final volume
2. Distilled water is added to the volumetric flask up to the line on its neck