topic 4 Flashcards
What is an indicator
a dye that changes colour depending on whether its above or below a certain pH
What can be used to measure the pH electronically
A pH probe attached to a pH meter
What is an acid
A substance that forms aqueous solutions with a pH of less than 7
What is a base
A substance with a pH greater than 7
Acid + base ——>
Salt + water
What ions do alkalis form in water
OH^-
What ions do acids form in water
H^+
What do acids do in water
- They ionise in aqueous solution
- they produce protons in water
What type of acids ionise completely in water
Strong acids
Weak acids do not fully ionise in solutions what does this mean for some acid particles
They dissociate to release H^+ ions
What is an electrolyte
A molten or dissolved ionic compound
What happens in electrolysis
An electric current is passed through an electrolyte
What do ions do in electrolysis
They move towards the electrodes, where they react, and the compound DECOMPOSES
What do positive ions do in the electrolyte
Move towards the cathode (-ve electrode) and gain electrons (they are REDUCED)
What type electrode do positive ions move towards
-ve electrode
What do the negative ions do in the eoectrolyte
Move towards the anode (+ve electrode) and lose electrons (they are OXIDISED)
What type of electrode do the negative ions move towards
+ve electrode
As ions travel to the electrodes what happens
It creates a flow of charge through the electrolyte
What happens as ions gain or lose electrons
They form the uncharged element and are discharged from the electrolyte
Why can’t an ionic solid be electrolysed
Because the ions are in fixed positions and can’t move
Why can molten ionic compounds be electrolysed
Because the ions move freely snd conduct electricity
What type of ionic compound can be electrolysed
Molten ionic compound
Positive METAL ions are … to the element at the …
- reduced
- cathode
Negative NON-METAL ions are …. to the element at the …
- oxidised
- anode
