Predicting the products at each electrode in aqueous solutions, the required practical, and writing half equations. Half equations are Higher tier.
You can study this deck without signing up — your progress is kept in this browser. An account saves it properly, syncs it across devices, and lets you edit the cards.
1.Which four ions are present when an ionic compound is dissolved in water?
The ions from the compound, plus hydrogen ions and hydroxide ions from the water itself.
2.What is produced at the cathode in an aqueous solution?
Hydrogen, unless the metal is less reactive than hydrogen, in which case the metal is produced.
3.Why is hydrogen usually produced at the cathode?
If the metal is more reactive than hydrogen, its ions stay in solution and the hydrogen ions gain electrons instead.
4.When is a metal produced at the cathode instead?
When the metal is less reactive than hydrogen, such as copper or silver.
5.What is produced at the anode if a halide ion is present?
The halogen: chlorine, bromine or iodine.
6.What is produced at the anode if no halide is present?
Oxygen, from the hydroxide ions.
7.Predict the products of electrolysing copper chloride solution.
Copper at the cathode, because copper is less reactive than hydrogen, and chlorine at the anode.
8.Predict the products of electrolysing sodium chloride solution.
Hydrogen at the cathode, because sodium is more reactive than hydrogen, and chlorine at the anode.
9.Predict the products of electrolysing copper sulfate solution.
Copper at the cathode and oxygen at the anode, since sulfate is not a halide.
10.Predict the products of electrolysing sodium sulfate solution.
Hydrogen at the cathode and oxygen at the anode.
11.How do you test for chlorine?
Damp litmus paper is bleached white.
12.How do you test for oxygen?
A glowing splint relights.
13.How do you test for hydrogen?
A lit splint gives a squeaky pop.
14.In the required practical, what is investigated?
What is produced at each electrode when different aqueous solutions are electrolysed.
15.Why are inert electrodes used in the practical?
Graphite and platinum do not react, so the products are only from the electrolyte and the results can be compared fairly.
16.What would you observe at the cathode with copper sulfate solution?
A pink-brown coating of copper builds up on the electrode.
17.What would you observe at the anode with copper sulfate solution?
Bubbles of gas form, which is oxygen.
18.Write the half equation for hydrogen ions at the cathode.
2H+ + 2e- gives H2
19.Write the half equation for copper ions at the cathode.
Cu2+ + 2e- gives Cu
20.Write the half equation for hydroxide ions at the anode.
4OH- gives O2 + 2H2O + 4e-
21.Write the half equation for chloride ions at the anode.
2Cl- gives Cl2 + 2e-
22.How do you check a half equation is correct?
The atoms must balance and the total charge must be equal on both sides.
23.Why do electrons appear on the left at the cathode but the right at the anode?
At the cathode ions gain electrons, so electrons are a reactant. At the anode ions lose electrons, so electrons are a product.
24.Why does the concentration of the solution change during electrolysis?
Ions are being removed and turned into products at the electrodes, so fewer remain in solution.
25.Why is electrolysis of brine industrially important?
It produces chlorine, hydrogen and sodium hydroxide, all of which are valuable raw materials.
26.A student electrolyses potassium bromide solution. Predict the products.
Hydrogen at the cathode, because potassium is more reactive than hydrogen, and bromine at the anode because bromide is a halide.
You remember far more by trying to recall an answer than by reading it. Run these as flashcards and the ones you keep getting wrong will come back more often.
Start studyingOr see the other Chemical Changes decks.