I am making a 0.1 M KCl (molar mass 74.551) solution for an experiment. To measure the mass of the KCl, I will use an analytical balance that is only accurate to ± 0.01 g. I place a piece of paper on the balance and set the tare to read 0.00. I then put the KCl on the balance until it reads 6.79 g. What is the uncertainty in this mass? 

• A. 0.010 g
• B. 0.014 g
• C. 0.0002 g
• D. 0.020 g

Answer: (B)

Verified step by step guidance

1. Understand that the uncertainty in a measurement is determined by the precision of the instrument used. In this case, the analytical balance has an accuracy of ± 0.01 g.
2. When measuring mass, the uncertainty is typically the smallest division or the precision of the balance, which is ± 0.01 g in this scenario.
3. Consider that the uncertainty applies to both the initial tare setting and the final mass measurement. Since the tare is set to 0.00 g, its uncertainty is also ± 0.01 g.
4. Combine the uncertainties from both the tare and the mass measurement. Since these are independent measurements, the uncertainties are added in quadrature: \( \sqrt{(0.01)^2 + (0.01)^2} \).
5. Calculate the combined uncertainty to determine the total uncertainty in the mass measurement of the KCl.