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Several questions in the homework ask for the pH of a weak acid given its initial concentration, so we would have to find the "x" value, which equals [H3O] and then find the negative log of that to find pH. However, I noticed that in the solutions and Dr.Lavelle's examples we round/do sig figs for the value of x before we even find the negative log of it to get pH. Why do we do that and why don't we wait until after solving for pH to do sig figs since the pH value would be the final answer?
I'm not sure, but I've heard from several TA's that it is important not to round any answers until the end because this is how they calculate the test answers. I'm not sure why they would round before getting the final answer, but to be safe I would complete the entire problem and only take sig figs at the end.
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