Calculations, Electrolysis

Question 1

What is the Relative Formula Mass for MgCl2?

Answer 1

24 + (35.5 * 2) = 95

Question 2

What does it mean if a salt is Anhydrous?

Answer 2

Salt doesn’t contain any water of crystallisation

Question 3

What does it mean if a salt is Hydrated?

Answer 3

A salt contains water of crystallisation

Question 4

What is Electrolysis?

Answer 4

• Breaking down of a substance using electricity
• Electric current passed through electrolyte causing it to decompose
• Oxidation and reduction occur

Question 5

What is Oxidation?

Answer 5

Loss of electrons

Question 6

What is Reduction?

Answer 6

Gain of electrons

Question 7

What are Ionic Half Equations?

Answer 7

Show how electrons are transferred during reactions

Question 8

How do you Write Half Equations?

Answer 8

• Put 1 thing as being oxidised/reduced on one side of arrow, the thing it gets oxidised it reduced to on the other
• Balance up number of atoms
• Add electrons (e^-) onto one side to balance up charge

Question 9

What are Molten Ionic Compounds?

Answer 9

• Electrolysed because ions move freely
• Broken into their elements
• E.g. molten lead bromide (PbBr2)

Question 10

How do you sort up an Electrochemical Cell for an Aqueous solution?

Answer 10

• Get 2 inert electrodes (graphite or platinum electrodes)
• Clean surface of electrode using emery paper (or sandpaper)
• Place electrodes into beaker filled with your electrolyte
• Connect electrodes to power supply using wires and crocodile clips
• Turn power supply on and a current will flow through cell

Question 11

What is an Electrochemical Cell?

Answer 11

• Circuit

* Made up of: anode, cathode, electrolyte, power source, wires that connect 2 electrodes

Question 12

How can you reduce a Metal Oxide (copper II oxide) to find its Empirical Formula?

Answer 12

• Place bung into test tube with hole at end, weigh using balance
• Take bung out and put copper(II)oxide in middle of tube
• Put bung in and weigh again
• Use Bunsen burner to heat copper(II)oxide until changes colour from black to pink
• Turn of heat and leave to cool
• One cooled, weigh test tube with bung and contents

Question 13

How can you find the Empirical formula using Combustion?

Answer 13

• Heat crucible to get it clean
• Cool it then weigh it (initial)
• Add magnesium ribbon,reweigh
• Mass of magnesium is this reading minus initial reading
• Heat crucible until magnesium turned white, lid on, leave small gap so oxygen can enter
• Cool it then reweigh
• Mass of magnesium oxide is this reading, minus initial reading