pH scale

Question 1

WHat is the equation for pH?

Answer 1

• pH = -log₁₀ [H+ (aq)]

Question 2

Why is pH used?>

Answer 2

• different way of stating [H+]
• using the logarithim of conc does away with awkwards small numbers
  
  • because [H+] is usually small
• minus sign used to make values positive

Question 3

WHat are the rules of the pH scale?

Answer 3

• smaller the pH, greater {H+]
• the difference of one pH number means a tenfold differrnce in [H+]

Question 4

How does a pH meter work?

Answer 4

• electrode which dips into a soln and creates a voltage relating to [H+]
• can be red of meter or fed into a computer or data logger for continuous montiroing of a chemical process

Question 5

How does pH measure alkilinity?

Answer 5

• as conc of [H+] increases, [OH-} goes down
• [OH-] > [H+] then the soln in alkalinbe

Question 6

What is the conc of water

Question 7

What is a strong acid?

Answer 7

• completely dissociated in soln
• therefore [HA] = 0M
• [H+] placed straight into log equation

Question 8

How can pH of a strong acid be a large number/

Answer 8

• refers only to extent of dissociation, and not to the conc