physical - acids&bases 2

Question 1

what is pH and how do we calculate it

Answer 1

pH is a measure of the concentration of hydrogen ions in a solution, it is a logarithmic scale

formula: pH = -log[H+]
or [H+] = 10^-pH

Question 2

what we assume from pH scale

Answer 2

1) the smaller the pH, the greater the concentration of H+ ions
2) a difference in one pH number means a tenfold difference in [H+]
e. g. pH 2 has 10 more H+ ions than pH 3

Question 3

strong acid

Answer 3

• a strong acid dissociates completely in water, releasing H+ ions

Question 4

how to calculate pH of strong acids

Answer 4

pH = -log[H+]

Question 5

solve: find the pH if 0.5 moles of HCl(g) is added to 1dm3 of water

Answer 5

• pH = -log[H+]
• pH = -log[0.5]
• pH = 0.30

Question 6

note about pH values

Answer 6

• they must always be given to two decimal places

Question 7

monoprotic, diprotic and triprotic acids

Answer 7

• monoprotic acid: gives one proton or hydrogen ion in aqueous solution
  HCl
• diprotic acid: gives two proton or hydrogen ion in aqueous solution
  H2SO4
• triprotic acid: gives three proton or hydrogen ion in aqueous solution
  H3PO4
• when calculating the pH, multiply [H+] according to the type of acid