Significant Figures (Help!)

Question

How many significants figures will the final answer have? For example, is the final answer just 2 g or is it 2.421g?

Calculate the mass of NaOH that must be dissolved in exactly 1L of solution so that 38.00 mL of this solution is required to titrate to the equivalence point of a solution containing 0.2744 g of a monoprotic acid with a molar mass of 119.3 g/mol. The molar mass of NaOH is 39.997 g/mol. Give your answer in grams with the correct significant digits.

Note: I don't need help solving the problem, I am just not sure how many significant figures my final answer will have based on the details in the problem. Thank you so much.

Answer 1

Hi Rachel!

For solving for a problem with significant figures ("sig figs"), you want to chose the part of the equation that has the least number of significant figures.

A good rule of thumb for zeros is that they count as "significant" if they are to the right of the decimal point (Eg. .002 has 3 sig figs). If a zero is to the left of the decimal, it DOES NOT count as a sig fig (1,000,000 could be rewritten as 1x10^6 and has one sig fig).

It looks like your numbers have a minimum of four sig figs. Therefore, your answer will have 4 significant figures, so it would be "2.421g" vs "2g"

1. 38.00 mL (4 sig figs)
2. 0.2744 g (4 sig figs)
3. 119.3 g/mol (4 sig figs)
4. 39.997 g/mol(5 sig figs)

Best of Luck!