A research intern weighs multiple samples of an unidentified organic compound and…
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A research intern weighs multiple samples of an unidentified organic compound and determines the corresponding number of moles with high-precision volumetric analysis. The results are shown below.
Amount, n (mol)
Mass, m (g)
0.0100
1.80
0.0200
3.61
| 0.0250 | 5.80 | ← Trial C
| 0.0300 | 5.42 |
| 0.0400 | 7.21 |
Trial C was performed late in the day when the balance room temperature fluctuated.
Answer the questions that follow.
(a) Sketch a properly labelled mass-versus-amount graph for the data. Circle any point that does not lie on the best straight-line trend suggested by the other measurements.
(b) Using all data except the anomalous point identified in part (a), determine the numerical value of the slope of the best-fit line and hence the experimental molar mass of the compound.
(c) Provide at least one reason, grounded in experimental chemistry, to justify treating Trial C as an outlier.
(d) Two candidate molecular formulas are proposed: glucose (C₆H₁₂O₆, 180.16 g mol⁻¹) and sucrose (C₁₂H₂₂O₁₁, 342.30 g mol⁻¹). Using your result from part (b), decide which formula is more consistent with the data and calculate the percent error relative to that formula.