Question

1. the following measurements were made to determine the density of a material whose value was, according to the handbook of chemistry and physics, 1.15 g/ml

trial #1 0.95 g/ml
trial #2 1.16 g/ml
trial #3 1.26 g/ml
a. make a general comment on the accuracy of these results
b. make a general comment on the precision of these results
c. use the average of the three trials as the “measured value” and determine the numerical value for the percent error.

Explanation:

a. Step1: Define accuracy

Accuracy: closeness to accepted value (1.15 g/mL).

a. Step2: Analyze trial values

Trials: 0.95 (low), 1.16 (close), 1.26 (high); spread indicates poor accuracy.

b. Step1: Define precision

Precision: closeness of trials to each other.

b. Step2: Analyze trial spread

Trials range 0.95-1.26 g/mL; large spread indicates low precision.

c. Step1: Calculate average of trials

Average = (0.95 + 1.16 + 1.26)/3

c. Step2: Compute average value

Average = 3.37/3 ≈ 1.1233 g/mL

c. Step3: Apply percent error formula

% Error = |(Average - Accepted)/Accepted| × 100%

c. Step4: Substitute values and calculate

% Error = |(1.1233 - 1.15)/1.15| × 100% ≈ 2.3%

Answer:

a. The accuracy is poor; trials show significant spread from the accepted value (1.15 g/mL).
b. The precision is low as trials have a large range (0.95-1.26 g/mL).
c. The percent error is approximately 2.3%.