MODULE 2

Question 1

Way to find gas given only volume and pressue

Answer 1

P1V1 = P2V2

Volume of gas at RTP = 24000cm3

Question 2

How to calculate molecular formula from empirical and MR

Answer 2

Work out the MR of the empirical formula and compare to the value given in the Q.

Question 3

How to find water of crystallisation

Answer 3

IS A REVERSABLE REACTION!

Find moles and then find ratio

Question 4

Concentrations of ionic solutions

Answer 4

1 mol of CaCl2 = 1 mol of Ca+ and 2 mol of 2Cl+

Question 5

Why might a reaction have a low yield?

Answer 5

• Reaction didn’t go to completion
• Transfer loss, separation loss
• Side reactions produce the wrong product

Question 6

Atom economy

Answer 6

Useful products/all reactants x 100

Better:
- Alternative reaction pathway
- Find uses for waste products

Question 7

Metal equations

Answer 7

Metal + acid -> salt + hydrogen
Metal oxide + acid -> salt + water
Metal hydroxide + acid -> salt + water
Metal carbonate + acid -> salt + water + carbon dioxide

Question 8

Titration calculations

Answer 8

Note down all values and write a balanced equation.

1. Find mol of known
2. Find ratio
3. Find concentration of alkali

Question 9

Oxidation states rules

Answer 9

• Elements & compounds add up to 0
• Ions add up to their charge
• Group 1 = +1 & group 2 = +2
• H = +1 except in metal hydrides, -1
• Oxygen is -2 except in peroxides or with fluorine

Question 10

Redox reactions

Answer 10

• Decrease in oxidation state = gain of electrons
• Increase in oxidation state = loss of electrons
• Disproportionation = both red and ox
  Cl2 + 2NaOH -> NaCl + NaClO + H2O

Question 11

Rules for redox half equations

Answer 11

• Balance oxygens with H2O
• Balance hydrogens with H+
• Balance charges with electrons
• When adding half equations, make e- numbers the same

Question 12

Properties of ionic structures

Answer 12

• Large lattices with electrostatic attraction
• High melting and boiling points - attraction requires a lot of energy to break
• Hard and brittle as the ions are fixed in place

NO LDF!!!

Question 13

Symmetrical molecules?

Answer 13

Forces balance each other out so the molecule is non-polar

Question 14

What affects the strength of LDF forces?

Answer 14

• Number of electrons
• Shape of molecule - straight molecules have more contact points, meaning stronger intermolecular forces & higher BP

Question 15

Properties of simple molecular structures

Answer 15

• Low melting and boiling points - intermolecular forces
• Insolulbe
• Do not conduct electricity