Question

1. to two significant figures, the measurement 0.0255 g should be reported as

a. 0.02 g.
b. 0.025 g.
c. 0.026 g.
d. 2.5 × 10² g. (some parts crossed out)

Explanation:

Step1: Recall significant figures rules

Leading zeros are not significant. So in 0.0255 g, the significant figures start from 2. The digits are 2, 5, 5 (after ignoring leading zeros).

Step2: Round to two significant figures

We look at the third significant figure (the second 5) to round the second significant figure (5). Since 5 ≥ 5, we round up the second significant figure. So 25 (from 0.0255, considering significant figures) becomes 26 when rounded to two significant figures. But we also need to consider the place. Alternatively, in scientific notation, 0.0255 g = \(2.55\times 10^{-2}\) g. Rounding \(2.55\times 10^{-2}\) to two significant figures gives \(2.6\times 10^{-2}\) g? Wait, no, wait. Wait, 0.0255: the first significant figure is 2 (position -2 in decimal, \(2\times 10^{-2}\)), second is 5 (\(5\times 10^{-3}\)), third is 5 (\(5\times 10^{-4}\)). To two significant figures, we take the first two significant figures (2 and 5) and round the second one based on the third. The third is 5, so we round the 5 (second significant figure) up. So 25 becomes 26? Wait, no, 0.0255: let's write it as 2.55 × 10⁻². Rounding to two significant figures: look at the third digit (5) in 2.55. Since 5 ≥ 5, we round the middle digit (5) up to 6? Wait, no, 2.55 rounded to two significant figures is 2.6? Wait, no, 2.55: first sig fig 2, second 5, third 5. So round the second sig fig (5) up by 1, so 5 becomes 6? Wait, no, 2.55: 2.5 (two sig figs) but the next digit is 5, so 2.5 + 0.1 = 2.6? Wait, no, 2.55 is closer to 2.6 when rounding to two significant figures? Wait, no, 2.55: the second decimal place (in 2.55) is 5, so when rounding to two significant figures (the 2 and 5), the third digit (5) tells us to round the 5 up. So 2.55 → 2.6 when rounded to two significant figures. But in the original number, 0.0255, the significant figures are 2,5,5. So two significant figures: 2 and 5, but we round the 5 up because the next digit is 5. So 0.0255 rounded to two significant figures is 0.026 g (option c) or in scientific notation \(2.6\times 10^{-2}\) g, but let's check the options. Option c is 0.026 g, option d was crossed out, option a is 0.02 (only one significant figure), option b is 0.025 (three significant figures? No, 0.025 has two significant figures? Wait, 0.025: leading zeros not significant, so 2 and 5 are significant, so two significant figures. But 0.0255 is 2.55 × 10⁻². Rounding 2.55 to two significant figures: 2.6 × 10⁻², which is 0.026. So the correct answer is c. 0.026 g.

Answer:

c. 0.026 g