How to estimate logs

[sdn_addict]

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Can anyone please teach me a simple way to estimate logs? 😕😕

For example, if pka=-log6.5 x 10^-5
pka ~4.2

or -log 2 x 10^-5= 4.7

Thanks!

 

[whoaaitzkyle]

Can anyone please teach me a simple way to estimate logs? 😕😕

For example, if pka=-log6.5 x 10^-5
pka ~4.2

or -log 2 x 10^-5= 4.7

Thanks!

pka=-log6.5 x 10^-5

Think of it like 5 - log6.5 and as the number (6.5 in this case) gets larger the answer gets closer to 1. So since 6.5 is a relatively large number (compared to 1 oe 2) we can estimate it will be around 4.2.

Same for -log 2 x 10^-5= 4.7.... you take 5-log2. log2 will be a smaller and further from 1 which means it will be closer to 5.

hope that helps!

 

[sdn_addict]

thanks for your help!

 

[chrisvocker]

I had the same problem you did....what whoaaitzkyle said is good advice.

Also, consider making a table of log 1 - 10

For example:

log 1 = 0
log 2 = .3
log 3 = .47

Just kinda be familiar with where the log is greater/less than 1/2 ... it will make your estimations more accurate

 

[sdn_addict]

I had the same problem you did....what whoaaitzkyle said is good advice.

Also, consider making a table of log 1 - 10

For example:

log 1 = 0
log 2 = .3
log 3 = .47

Just kinda be familiar with where the log is greater/less than 1/2 ... it will make your estimations more accurate

yea i think i'll do that and memorize. thanks for your advice.