Chemistry Clarity · chemistryclarity.com

Significant Figures: Flashcards

Revise counting significant figures, scientific notation, rounding, and accuracy versus precision.

14 cardsBeginner

14 cards

  1. Question
    What are significant figures?
    Answer

    The digits in a measurement that are known with certainty, plus one estimated digit.

  2. Question
    How many significant figures in 0.0042 L?
    Answer

    2 (leading zeros are not significant)

  3. Question
    How many significant figures in 2.500 mL?
    Answer

    4 (trailing zeros after a decimal point are significant)

  4. Question
    How many significant figures in 1.05 m?
    Answer

    3 (a zero between non-zero digits is significant)

  5. Question
    Rule for multiplying and dividing?
    Answer

    The answer has the fewest significant figures of the measured inputs.

  6. Question
    Rule for adding and subtracting?
    Answer

    The answer has the fewest decimal places of the measured inputs.

  7. Question
    Write 0.000 520 m in scientific notation.
    Answer

    5.20×10−45.20 \times 10^{-4} m (3 significant figures)

  8. Question
    Do exact numbers (such as 1 km = 1000 m) limit significant figures?
    Answer

    No. Exact numbers have unlimited significant figures.

  9. Question
    What is the difference between accuracy and precision?
    Answer

    Accuracy: closeness to the true value. Precision: closeness of repeated measurements to each other.

  10. Question
    25.12 g + 3.4 g = ?
    Answer

    28.5 g (one decimal place, like 3.4 g)

  11. Question
    Round 2.345 g and 2.355 g to three significant figures.
    Answer

    2.34 g and 2.36 g. An exact 5 is rounded to the even digit (round half to even).

  12. Question
    Why are measurements made in replicate (e.g. triplicate or quintuplicate)?
    Answer

    One measurement cannot show its precision. Replicates give a mean (best value) and a standard deviation (precision).

  13. Question
    Which statistic measures accuracy and which measures precision?
    Answer

    Accuracy: the error, mean − true value. Precision: the standard deviation (or relative standard deviation).

  14. Question
    Which kind of error lowers accuracy but not precision?
    Answer

    A systematic error, e.g. a badly calibrated balance shifts every result the same way.