How can I determine if a 10^-9 M NaOH aqueous solution is acidic or neutral?

Please explain.

Expert Answers

An illustration of the letter 'A' in a speech bubbles

The solution can be considered as a neutral solution. In order to determine its pH we should get the concentration of OH- in the solution. 

We first let a 1 liter of solution of 10^-9 M NaOH.

In a liter of solution there are 10^-9 moles NaOH thus there are 10^-9 moles OH- (Since moles NaOH = moles Na+ = moles OH-).

Next, remember that neutral water has 10^-7 moles OH or H+ right? So we add the moles of NaOH with the moles of OH derived from water.

10^-9 + 10^-7 = 1.01x10^-7 moles NaOH

pOH = -log (OH-)

pOH = -log (1.01x10^-7)

pOH = 6.99

pH = 14 - pOH

pH = 14 – 6.996

pH = 7.004 ~ 7.00 therefore neutral.

See eNotes Ad-Free

Start your 48-hour free trial to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Get 48 Hours Free Access
Approved by eNotes Editorial