Acid-Base and pH

Question 1

Arrhenius acid and base

Answer 1

Acid - Produces hydrogen ion
Base - Produces hydroxyl ion and cation in water

Question 2

Bronsted lowry acid and base

Answer 2

Acid - Proton donor
Base - Proton acceptor

Question 3

Conjugate base pairs

Answer 3

• Acid reacts with base to produce a conjugate base to produce conjugate acid
• Strong acid had weak conjugate base

Question 4

Ka relationship with acid strength

Answer 4

Completely disassociate in new solution bigger Ka value

Question 5

Ka equation

Answer 5

• -log(Ka) is the pKa
• Bigger Ka over the smaller Ka to see how much bigger it is

Question 6

Acidity

Answer 6

More electronegative element help stabilise the negative charge

Question 7

Basicity

Answer 7

Decrease electrons for more electronegative elements less likely to be donated

Question 8

Acidity with electron withdrawing group

Answer 8

• Electron withdrawing groups (Br, Cl, F) attract electrons from negatively charged atom of the conjugate base pair which stabilises it
• Decrease pKa when you increase number of electron withdrawing increase acidity
• When electron withdrawing group is closer to the -OH pH increases less acidic

Question 9

Acidity with Electron donating groups

Answer 9

Longer carbon chains destabilise increase electron density so weaker acid & increased pH

Question 10

Basicity with electron groups

Answer 10

• Electron withdrawing destabilising conjugate acid less likely to pick up proton decrease basicity
• Electron donating groups increase basicity nitrogen increase protonation

Question 11

Hybridising effect and acidity

Answer 11

• Acidity in pH the sp electrons are held closer the conjugate base pairs more stable
• Sp3 (single bond) 25%s character less acidic compared to Sp2 33%s (double bond) and 50%s for sp (triple bond) orbital
• The lone pair on sp and sp2 are held closer so more difficult to protonate than sp3 so sp3 more basic high pH

Question 12

Hybridisation

Answer 12

• S represents Hydrogen bond
• Sp represents a triple bonded carbon
• Sp2 represents a double bonded carbon
• Sp3 represents a single bonded carbon

Question 13

Resonance

Answer 13

• Delocalisation of charge in conjugate base anion is a stabilising factor increase acidity of acetic acid to ethanol
• Due to delocalisation of charge in acetate and not ethanol where its localised
• Acidity of C-H further enhanced if 2 carbonyl groups
• Delocalised enables charge to be transferred to electronegative oxygen atom
• Cyclohexanol and phenol difference of delocalisation of negative charge to aromatic ring so pH lower in acids
• Sp2 more electronegative than sp3