Significant Figures in Equilibrium calculations

[emilie liu 3G]

When calculating pH in titrations of buffers, should we still follow the rule where we carry all significant figures and round at the end? I have been doing some practice problems using that rule and have been off a tenth or two usually. When I look at the solutions manual and practice finals, it looks like they round and cut of the intermediate values at the correct significant figures at each step. Additionally, when there is addition and subtraction involved, simply looking at the initial significant figures would not work because the sig fig rules are different when addition and subtraction are involved right?

[Emily_Lenh2A]

I believe that we should still follow the rule in which we round at the end instead of rounding after every step, since that's what they told us to do before on the quizzes and midterm. I think that the practice midterm had rounded after every step as well, but I generally disregarded that and did what they told us to do on the actual midterm. Regarding the rules for sig figs for addition and subtraction, you're supposed to use the smallest number of decimal places in the calculation. (For example, 123.2+123.22 would equal 246.4 rather than 246.42.) Hope this helps!

[604805638]

The rules are also all in the beginning of the course reader if you need help remembering them

[emilie liu 3G]

I understand the rules of significant figures. I was asking if we simply carry all the significant figures and round at the end like usual or round at each individual step because the solution manual and practice finals derive their answers by rounding each individual step. When I followed the usual rules of significant figures, I got different answers than the manual.