Question

A chemist needs to know the mass of a sample of aniline to 3 significant digits. She puts the sample on a digital scale. This is what the scale shows:

100.4 If this measurement is precise enough for the chemist, round it to 3 significant digits.

A. 100.4
B. 100
C. 100.0
D. No solution

Answer 1

The mass of aniline shown on the scale is 100.4, which already contains four significant digits. When rounded to three significant digits, the value stays the same as 100.4 (option A), as the digit after the decimal is less than 5.

Step-by-step explanation:

The chemist needs to round the mass of aniline to three significant digits. The measurement shown by the digital scale is 100.4. When rounding to three significant digits, this value already has four significant digits. However, since the value after the decimal is less than 5, when we round it to three significant digits, it should remain the same, i.e., 100.4. Therefore, the correct answer is 100.4, which is option A.

It is important to note that significant figures should be maintained throughout a calculation process, and only at the end should the final answer be rounded to reflect the least certain measurement. This helps to minimize rounding errors and potential inaccuracies in the final reported value.