1.2Amount Of Substance

Question 1

Define relative atomic mass

Answer 1

The average mass of a molecule/element, compared to 1/12th of a Carbon-12 atom

Question 2

What is the Avogadro constant?

Answer 2

The number of atoms in a mole of a substance

6.022x10^23

Question 3

What equation can be done to work out moles?

Answer 3

Mass = Mr Moles

Question 4

How can you find out the moles of a substance (involving concentration)

Answer 4

Moles = concentration x volume

Question 5

What is the ideal gas equation ?

Answer 5

PV=nRT
Pressure
Volume
Number of moles
Gas constant 
Temperature

Question 6

What are the units that should be used in the ideal gas equation ?

Answer 6

Pressure (Pa)
Volume (m^3)
Temperature (K)

Question 7

What is empirical formula?

Answer 7

The simplest whole number ratio of atoms in a compound

Question 8

Describe how to find empirical formula.

Answer 8

• Mass of each atom divided by Mr to find moles
• Divide each atom’s moles by the atom with the smallest no of moles
• calculate a ratio that gives whole numbers.

Question 9

What is the equation of atom economy?

Answer 9

Molecular mass of desired product divided by sum of molecular mass of all reactants

Question 10

What is the mole in terms of gasses?

Answer 10

1 mole of a gas occupies 24dm^3 at room temperature and pressure

Question 11

How do you write full ionic equations ?

Answer 11

By splitting up all the aqueous species into their ions, and writing the equation like that, eg
NaOH + HCl -> NaCl + H2O
Na+ + OH- + H+ + Cl- -> Na+ + Cl- + H2O

Question 12

How do you write simplified ionic equations ?

Answer 12

You do the same for full ionic equations, but remove any of the ions that are on both sides. Eg.
Na+ + OH- + H+ + Cl- -> Na+ + Cl- + H2O
OH- + H+ -> H2O

Question 13

How do you calculate the limiting reagent of an equation?

Answer 13

Calculate the moles of both reagent, and the reagent with the smallest moles (considering the ratio) is the limiting reagent.

Question 14

How do you calculate the percentage yield?

Answer 14

Mass of product obtained divided by the maximum theoretical mass of product

Question 15

What is a back titration?

Answer 15

A back titration is done to analyse a base/acid that does not react easily or quickly with an acid/base. The base is treated with an excess of acid, and the the left over acid is titrated. You can then work back to find out the original base.