C3.3 Flashcards
What is a redox reaction?
A reaction where a reduction and oxidation occurs at the same time
What is a reduction?
Loss of oxygen from a substance or gain of electrons
What is oxidation?
Gain of oxygen by a substance or loss of electrons
What is reducing agent?
The compound that reduces the other (removes the oxygen from the substance to itself)
What is the oxidising agent?
The compound that oxidised the other (it is getting reduced by oxidizing the other)
What is an acid?
Substance that releases hydrogen ions when dissolving in water to make an aqueous solution
What is a base?
Substance that neutralises acids
If a base can dissolve in water it is also an alkali
What is an alkali?
Releases hydroxide ions when dissolving innwsyer to form an aqueous solution
What is the pH of an acid?
pH < 7
What is the pH of a neutral solution?
pH = 7
What is the pH of an alkaline?
pH > 7
What is neutralization?
Reaction between an acid, base or an alkali to form a salt and water only
Salt made depends on the acid and base used
ACID + BASE > SALT + WATER
How does the pH change depending on what is added to what?
If a base/alkali is added to an acid the pH goes from less than 7 to greater than 7
If an acid is added to a base/alkali the pH goes from greater than 7 to less than 7
How can you predict the salt made?
If you know the acid and base/alkali used
The salts have two parts:
- first part is from the metal in the base or alkali
- second part comes from the acid used
What happens during neutralization in solution?
Acids contain hydrogen ions
Alkaline solutions contain hydroxide ions
These react together to produce water
H + OH > H2O
What happens when acids react with carbonates?
ACID + CARBONATE > SALT + WATER + CARBON DIOXIDE
The carbon dioxide is released as bubbles in the acid during the reaction
What is effervescence?
Bubbling or fizzing
What happens when acids react with metals?
ACID + METAL > SALT + HYDROGEN
The hydrogen is released as bubbles in the acid
What is a dilute and concentrated acid?
Dilute acid = low ratio of acid to volume of solution
Concentrated acid = contains a high ration of acid to volume
What are weak and strong acids?
Weak = partially ionized (only a small fraction of the molecules release hydrogen ions in an aqueous solution)
Normally not completed reactions (reversable arrow)
Strong = fully ionized (all molecules release hydrogen ions)
How is pH linked to hydrogen ion concentration?
In an aqueous solution as the concentration of H ions increases by a factor of 10 the pH decreases by 1
What pH would a concentrated acid have?
Lower pH
What pH would a strong acid have?
Lower pH
What is a pH titration curve?
Shows the effect on pH of changing the hydrogen ion concentration during a neutralisation reaction
How to do the experiment to draw a pH titration curve?
1) transfer 25cm^3 of dilute alkali to a beaker
2) estimate its pH using universal indicator solution and a colour chart or measure with a pH meter
3) add 1cm^3 of dilute acid, stir and record the pH
4) continue until you’ve added an excess of acid
5) plot a graph of pH against volume of acid added
