E21b Textbook Sig Fig Clarification

[Naman Jain 3F]

For E21b in the textbook, I noticed the answers in the solution manual had 3 sig figs. However, the starting amount of the compound is 25.92 mg which is 4 sig figs. I'm confused why the answer has 3 sig figs if we're starting out with 4 sig figs.

[Ysabelle Magat 1E]

Hi,

Sig figs refer to the digits following the decimal point; therefore, 25.92 has two sig figs and the answer (1.30x10^-3 and 7.83 x 10^20) also has two sig figs.

Hope this helps :)

[Ethan Hung 2A]

Hi Naman,
Your understanding of significant figures is correct as the answers should have 4 sig figs for 21b; the textbook may have an error. Regardless, do not worry too much -- I would imagine the midterms will not have these types of mistakes.

[Hannah_Pon_1F]

Hi,
For a little more clarification, the sig fig rules are different depending on the type of calculations being done. With addition and subtraction, the final answer's decimal places should match the smallest number of decimal places in the given data. While for multiplication and division, the final answer's number of sig figs should match the data value with the lowest number of sig figs. And for rounding, it is best to do it at the end of the calculation to ensure accuracy.

Hope this helps!

[Naman Jain 3F]

Hi,

Sig figs refer to the digits following the decimal point; therefore, 25.92 has two sig figs and the answer (1.30x10^-3 and 7.83 x 10^20) also has two sig figs.

Hope this helps :)

If I'm not mistaken, the digits in front of the decimal point are considered to be sig figs as well.

[Naman Jain 3F]

Hi Naman,
Your understanding of significant figures is correct as the answers should have 4 sig figs for 21b; the textbook may have an error. Regardless, do not worry too much -- I would imagine the midterms will not have these types of mistakes.

Thanks for your response Ethan! That's what I thought too because past problems I've done always match the sig figs of the beginning amount to the end amount.

[Naman Jain 3F]

Hi,
For a little more clarification, the sig fig rules are different depending on the type of calculations being done. With addition and subtraction, the final answer's decimal places should match the smallest number of decimal places in the given data. While for multiplication and division, the final answer's number of sig figs should match the data value with the lowest number of sig figs. And for rounding, it is best to do it at the end of the calculation to ensure accuracy.

Hope this helps!

Thanks for this helpful information! Since we were solely multiplying, I also thought that the sig figs would be 4 since that was the lowest number of sig figs in a data value.

[Ysabelle Magat 1E]

Hi,

Sig figs refer to the digits following the decimal point; therefore, 25.92 has two sig figs and the answer (1.30x10^-3 and 7.83 x 10^20) also has two sig figs.

Hope this helps :)

If I'm not mistaken, the digits in front of the decimal point are considered to be sig figs as well.

Oh I see where my mistake was; I confused the rules of sig figs because when the number is less than 1 (like 0.50 or something like that) the numbers following the decimal are significant (unless the number is 0.0500 then the 0 in between the decimal and the 5 are not significant). Sorry for the confusion!