C6 Flashcards
What do acids from in water?
H+ ions
What do alkalis form in water?
OH- ions
What pHs are considered acids?
0-6 pH
What pH is considered neutral?
7
What pHs are considered alkalis?
8-14 pH
What is the relationship between pH and concentration of H+ ions?
They are inversely proportionate, meaning as concentration of H+ ions increases, pH decreases
What is universal indicator?
A combination of dyes which when added to a solution, changes colour according to the pH
What happens if H+ concentration increases by a scale factor of 10?
The pH decreases by 1
Example question:
A solution with a H+ concentration of 0.001 mol/dm has a pH of 3. Predict the new pH if the H+ concentration is increased to 0.01 mol/dm.
The H+ concentration has increase by a scale of 10, therefore the pH decreases by 1. 3 - 1 = 2
Answer: 2
How can you estimate the pH of a solution from the concentration of H+ ions when in the unit mol/dm?
The pH will roughly be equal to the amount of 0s behind the first non zero number- for example the pH of 0.001 mol/dm will be 3, as there are 3 zeros before the 1
Example question:
Estimate the pH of a solution with a H+ concentration of 0.00023
There is 4 zeros before the 2, therefore the pH is 4.
Answer: 4
What is the difference between stronger and weaker acids?
In stronger acids, a higher proportion of acid molecules dissociate to release H+ ions.
In weaker acids, a lower proportion of acid molecules dissociate to release H+ ions.
What is the difference between an acids strength, and an acids concentration?
Strength is the proportion of how many acid molecules dissociate to make H+
Concentration is the amount of dissolved acid molecules in a set volume
In what reaction are salts formed?
Neutralization reactions
Are salts ionic compounds?
Yes
Acid + Metal Hydroxide –>
Salt + Water
Acid + Metal –>
Salt + Hydrogen
Acid + Metal Carbonate –>
Salt + Water + Carbon Dioxide
What are soluble salts?
Salts that can’t dissolve in water
What is a soluble salt?
A salt that can be dissolved in water
Describe the process of making a soluble salt using neutralization
1) You must measure the exact amount of alkali needed to neutralize the acid (or vise versa) by carrying out a titration
2) Next, carry out the reaction with the exact right proportions
3) The solution that remains after the reaction is over contains only salt and water
4) Slowly evaporate some of the water off and then leave the solution to crystallize
5) Filter off the solid
6) Finally, dry the salt
What is an insoluble salt?
A salt that cannot be dissolved in water
Describe the process of making a soluble salt using an acid and an insoluble reactant
1) Add the insoluble substance to the acid- they will react to produce the soluble salt
2) When the excess solid has sank to the bottom of the flask, the reaction has finished
3) Filter out the excess solid so only the salt and water is left
4) Evaporate some of the water off, then leave the salt to crystallize
5) Filter off the solid
6) Finally, dry the salt
How do you make a insoluble salt?
If you react 2 soluble salts, a insoluble salt (precipitate) will be made
