Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
29 Cards in this Set
- Front
- Back
|
What can be used to measure standard electrode potential? |
A standard half cell |
|
|
What are the standard conditions? |
25 degrees c 1.00 moldm-3 1 atm |
|
|
What does a half cell contain? |
The species from the half equations in equilibrium with each other under standard conditions. |
|
|
What are the 3 type of standard half cells? |
Metal ion/metal Metal ion/metal ion Non-metal/non-metal ion |
|
|
What is there in a metal ion/metal half cell? |
An electrolyte and a reactive metal electrode |
|
|
What is an electrolyte? |
A solution containing the dissolved metal ions |
|
|
What happens in a metal ion/metal half cell? |
The transfer of electrons (redox) takes place at the surface of the metal, which acts as an electrode |
|
|
Why must a metal be used as an electrode? |
It has free delocalised electrons |
|
|
What must you make sure you label in diagrams? |
Standard conditions |
|
|
What happens in a metal ion/metal ion half cell? |
A platinum electrode is used to make electrical contact with the ions in solution as it's inert. Redox takes place on its surface. The different species of metal ions are mixed in solution |
|
|
What happens in a non-metal/non-metal ion half cell? |
A platinum electrode is used to make electrical contact between the non-metal element and its aqueous ions. |
|
|
What happens if the non metal is a solid or gas? |
If it's a gas, glassware must be used to trap it. If it's a solid, it must be in contact with the electrode. |
|
|
Which is the only metal that is liquid at room temperature? |
Mercury |
|
|
Which is the only non-metal that is liquid at room temperature?
|
Bromine |
|
|
How is a standard hydrogen half cell set up? |
H2 (g) is trapped using glassware and bubbled through a solution of H+ ions. A platinum electrode is used |
|
|
Why is it sometimes difficult to use platinum? |
It's expensive |
|
|
What is the equation for the reaction in a hydrogen half cell? |
2H+ + 2e- <--> H2 |
|
|
What can be used as electrolytes and what are the concentrations? |
HCl, conc= 1.00moldm-3 H2SO4, conc= 0.500 moldm-3 |
|
|
Define standard electrode (redox) potential of a half cell |
The e.m.f of a half cell compared with a standard hydrogen half cell at standard conditions |
|
|
What must be done to measure the standard electrode potential of a half cell? |
The half cell must be connected to a standard hydrogen half cell by a salt bridge. Standard conditions must apply Eᶿ is measured in volts (V) from a high resistance voltmeter |
|
|
What is Eᶿ of the hydrogen half cell? |
0.00V |
|
|
What connects the 2 electrodes? |
A wire |
|
|
What does the salt bridge across the electrolytes do? |
Completes the circuit and allows the movement of ions between the 2 half cells |
|
|
How does electric current flow through the circuit? |
Electrons flow across the electrodes and wire, ions flow across the solution |
|
|
What is usually used for the salt bridge? |
Filter paper soaked in an ionic solution (which doesn't react with either electrolyte) |
|
|
What are 2 examples of these solutions? |
KNO3(aq) and NH4NO3 (aq) |
|
|
When is an electrochemical cell made? |
When any 2 half cells are connected by a salt bridge |
|
|
Why can't a conducting wire be used for the salt bridge? |
The metal wire may react with ions in the solution or the electrolyte. Ions can't move through solid metal |
|
|
What would the standard concentration for H+ be if H2SO4 was used and why? |
0.5 moldm-3 because there are 2 H+ ions for every H2SO4 |
