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Teaching Methods

Significant Figures on AP Exam

Started 3 months ago by Kimberly Duncan.


One more post about the AP Exam webinar last week - everyone's favorite topic - significant figures! We had two questions: Is every calculation evaluated for correct number of significant figures? If the Ka answer is given as 6.80 x 10-4, instead of 6.81 x 10-4, will that still get a point? Please post a reply if you have any words of wisdom. Thanks.


1 Comment

  • Linda Cummings

    Posted 2 months ago

    Only one of the answers within all of the FRQs is graded for sig figs. In the past, there was a +1/-1 leeway, but that is no longer the case. In general, the point has been on a lab question, but there is no guarantee that will continue. I recommend holding students to using correct sig figs as much as possible, realizing that on the exam, they will only be one point out of 46.

    "If the Ka answer is given as 6.80 x 10-4, instead of 6.81 x 10-4, will that still get a point?" Most likely yes. We are not worried about slight differences in final answers caused by rounding (at the end vs. at every step, or when looking up molar masses). We care more about the chemistry - is the calculation set up correctly? In fact, a "correct" answer earns no points without work shown.