[SimoneMeyer]

I've been asked to find the concentration of hydronium ions in the following substances:
a) a cleaning product that has a pH of 11,00.
b) black coffee which has a pH of 5,00

Here are my calculations:

a)

= 10 ^-pH
= 10 ^-11,00
= 1 x 10 ^-11 mol/L

b)

= 10 ^-pH
= 10 ^{- 5,00}
= 0.00001 mol/L


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The answer that I got for b) seems to be off for some reason. Not that I know why, but shouldn't it have something along the line of a "x 10 ^-1" or something? Or is it okay just like that? I may just be wasting your time and am sorry, but for some reason it looks wrong.

Also, for a) , is that the correct answer?

Thank you for your time!

[Borek]

That's OK, you may write it as 1x10^-5 if you prefer.

[SimoneMeyer]

Thank you!