calculate logs?

[HurricaneAlana]

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Ok... I understand that i the concentration [H] is 1 x 10^-3 then pH is 3 (correct?)

but I keep coming across problems just as 14 in GChem in Destroy were you have to know pOH= -log [2 x 10^-4]

I am able to get to that point, but how do I figure that out to be pOH=3.7 without a calculator? Is there something I'm missing? I don't see how I'd be able to do this on the DAT

Thanks!

 

[poc91nc]

Ok... I understand that i the concentration [H] is 1 x 10^-3 then pH is 3 (correct?)

but I keep coming across problems just as 14 in GChem in Destroy were you have to know pOH= -log [2 x 10^-4]

I am able to get to that point, but how do I figure that out to be pOH=3.7 without a calculator? Is there something I'm missing? I don't see how I'd be able to do this on the DAT

Thanks!

pOH = 4 - log2 = 3.7

log2 ~ 0.3
log3 ~ 0.5
log5 ~ 0.7
log7 ~ 0.8

Memorize those...and you will be able to do most log calculations easily.

 

[HurricaneAlana]

ohh!! good to know.. thanks so much!