Electrolysis and Reactivity Series by Nicholas Law

2.29 Reactivity Series (from high to low) :

2016-09-05 04:28:06 UTC

Potassium, Sodium, Lithium, Calcium, Magnesium,Aluminium,(Carbon), Zinc, Iron, (Hydrogen), Cooper, Silver, Gold

2.30 describe how reactions with water and dilute acids can be used to deduce the following order of reactivity: potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper

2016-09-05 04:30:35 UTC

Metals above hydrogen = reacts with WATER
Metal + cold water= Metal Hydroxide + Hydrogen
^ Magnesium doesn't react with cold water so metals above magnesium react.

Metal + Steam= Metal Oxide + Hydrogen

Example:
Calcium + Water - forms Calcium hydroxide which is not soluble. When it dissolves, it becomes colorless.

Ca(s) +2H2O (l) ---------> Ca (OH)2 (aq) + H2 (g)

1.48 understand that an electric current is a flow of electrons or ions

2016-09-05 04:31:17 UTC

An electric current is a flow of electrons and ions

2.35 describe how the rusting of iron may be prevented by grease, oil, paint, plastic and galvanizing

2016-09-05 04:31:39 UTC

Grease, oil, paint and plastic all act as a physical barrier when used to prevent iron from rusting.
Galvanizing iron is when you coat the metal in a layer of zinc. Even when the zinc surface is scratched, the iron doesn't rust because the zinc corrodes instead.
Zinc loses electrons to form zinc ions --> electrons flow into the iron, preventing it from rusting

1.49 understand why covalent compounds do not conduct electricity

2016-09-05 04:31:47 UTC

Covalent compounds do not conduct electricity because they don't have any mobile charged ions. They consist of atoms or molecules that are neutrally charged.

1.50: Understand why ionic compounds only conduct electricity when when molten or in solution.

2016-09-05 04:34:21 UTC

Ionic compounds have charged particles. They can only conduct electricity when molten or in aqueous/liquid state. Only then can ions move.

1.51: Describe experiments to distinguish between electrolytes and non-electrolytes

2016-09-05 04:36:54 UTC

A liquid or solution that conducts an electricity is known as an electrolyte.

Graphite is used because it's inert. If an ammeter is connected and a current is detected then the substance is an electrolyte.

2.31-2.33 deduce the position of a metal within the reactivity series using displacement reactions between metals and their oxides, and between metals and their salts in aqueous solutions; understand oxidation and reduction as the addition and removal of oxygen respectively; understand the terms redox, oxidising agent, reducing agent

2016-09-05 04:39:20 UTC

A METAL HIGHER IN THE REACTIVITY SERIES DISPLACES A LOWER METAL COMPOUND.

Mg (s) + CuO (s) ------> MgO (s) + Cu (s)

Magnesium is oxidized, it is the reducing agent.
Copper is reduced, it is the oxidizing agent.

A redox reaction is where both oxidization and reduction occurs.

1.52: Understand that electrolysis involves the formation of new substances when ionic compounds conduct electricity.

2016-09-05 04:40:40 UTC

When an electrolyte conducts

2.36 understand the sacrificial protection of iron in terms of the reactivity serie

2016-09-08 09:14:15 UTC

Zinc or magnesium blocks are often attached to large works of iron (ex: metal hulls, pipelines) to prevent the iron from rusting.
This works because both zinc and magnesium are higher up in the reactivity, so they corrode first.
The electrons produced as the more reactive metals are ionized, move into the iron and prevent it from ionizing.
This is called sacrificial protection.

2.34 describe the conditions under which iron rusts

2016-09-08 09:42:21 UTC

Iron rusts in the presence of both oxygen and water
*rusting can be accelerated in the presence of electrolytes such as salt*

1.53 describe experiments to investigate electrolysis, using inert electrodes, of molten salts such as lead(II) bromide and predict the products

2016-09-08 09:48:27 UTC

lead(II)bromide melts
bulb lights up --> indicates flow of electrons
bubbling around anode <-- brown bromide gas given off
nothing seems to be happening at cathode --> later metallic lead found underneath it
stop heating --> lead(II)bromide solidifies --> no more bubbling and bulb goes out

TRIPLE POINT 1.54 describe experiments to investigate electrolysis, using inert electrodes, of aqueous solutions such as sodium chloride and predict the products

2016-09-08 10:01:25 UTC

Cathode:

both Na+(aq) and H+(aq) are attracted to cathode
H+(aq) gets discharged because accepts electron easier than Na+(aq)
Hydrogen atoms formed combine to make hydrogen molecules (hydrogen is from water molecules splitting up)
hydroxide ion is also produced: H2O(l) --> H+(aq) + OH-(aq)

Anode:

Cl-(aq) and OH-(aq) both attracted to anode
hydrogen ion slightly easier to discharge than chlorine ion
there are a lot more chlorine ions though, so it's mainly those that get discharged

TRIPLE POINT 1.54 describe experiments to investigate electrolysis, using inert electrodes, of aqueous solutions such as copper(II) sulfate and dilute sulfuric acid and predict the products

2016-09-08 11:04:06 UTC

Copper(II) Sulfate
Cathode:

copper(II) ions and hydrogen ions will we attracted to the cathode
cooper is below hydrogen in the reactivity series, which means the copper ion will be easier to discharge
carbon electrode will be coated with brown copper

Anode:

Sulfate ions and hydroxide ions (from the water) will be attracted to the anode
sulfate ions are stable and aren't discharged
hydroxide ions are discharged and oxygen is produced

*once all the copper is used up, the solution will turn from blue to colorless and since the hydrogen ions and sulfate ions aren't being discharged, the solution turns into dilute sulfuric acid*

Dilute Sulfuric Acid
Cathode:

hydrogen ions from the water and the acid are attracted to the cathode
they're discharged to form hydrogen gas

Anode:

sulfate ions and hydroxide ions are attracted
sulfate ions are too stable to be discharged, so oxygen is produced from the discharge of hydroxide ions from the water

1.55 write ionic half-equations representing the reactions at the electrodes during electrolysis

2016-09-08 11:17:03 UTC