Acids and bases

Question 1

What is the definition of a strong acid?

Answer 1

Acid that fully dissociates

Question 2

What is the definition of a weak acid?

Answer 2

Acid that partially dissociates use reversable sign in equations

Question 3

Write the equation for calculating Ph using acid concentration.

Answer 3

Ph= -Log(H+)

Question 4

How do you work out acid concertation when a molecule has the OH- ion?

Answer 4

Use the Kw formula where Kw is a constant. Kw/(OH-)

Question 5

What is the definition of a conjugate base?

Answer 5

Two species differing by a H+ ion

Question 6

What does Ka stand for?

Answer 6

Weak acid dissociation constant

Question 7

Ka equation.

Answer 7

Ka=(H+)(product 1)/ (Reactants)

Question 8

If Ka is less than 1 acid is ? likewise if it is bigger than 1?

Answer 8

weak, it is strong.

Question 9

For weak acids what is the equation at equilibrium?

Answer 9

(H+)=(A-)

Question 10

What is a monobasic acid?

Answer 10

One mole of (butanoic) acid donates/dissociates to form one mole
of protons/H

Question 11

What is a buffer?

Answer 11

A system that minimises change in the Ph when small amounts of acid or alkali are added.

Question 12

What is different between the 2 methods to calculate buffer solution?

Answer 12

-method one is acid + substance
-method two is acid + base i.e __ hydroxide, carbonates, ammonia

Question 13

Explain how to do method 2.

Answer 13

-Calculate mols of both acid and base.
-Calculate the mols in excess, subtracting. Excess mols are known as [A-]
-Calculate conc of [HA] by doing excess mols/total volume
-Calculate conc of [A-] by doing [A-] mols/ total volume
-Replace in H+ equation and calculate Ph

Question 14

When is pKA used?

Answer 14

-When Ka value is very large for weak acids, the values themselves are smaller numbers.

Question 15

Define Equivalence point

Answer 15

-Centre point of the vertical section of the titration.

Question 16

What is the set method used to measure ph.

Answer 16

-Set up the equipment like you would for a titration and add 25cm^3 of acid in the conical flask
-Place the electrode of the pH meter in the flask after this has been calibrated and washed with distilled water
-Fill the burette with a base and add to the flask 1cm^3 at a time. Record pH values with the volume and swirl each time.
-Keep adding until the pH changes rapidly and keep adding until the pH changes less rapidly and the base is in excess
-plot graph against volume of base