Chapter 34 Multiple choice questions

1. An analyst determines the amount of contaminant in samples of steel as 1.0, 1.1, 1.3, 1.3, 1.4, 1.5, and 1.5 ppm.
What is the variance in ppm?

0.22 (to 4 s.f.)

−3.172 10⁻¹⁷(to 4 s.f.)

1.69 (to 4 s.f.)

0.03143 (to 4 s.f.)

2. An analyst determines the concentration of a pathogen in an athlete's blood as 12.0, 13.1, 14.3, 16.3, 21.4, 21.5, and 31.5 ppm.
What is the standard deviation in ppm?

20.81 (to 4 s.f.)

4.311 (to 4 s.f.)

519.5 (to 4 s.f.)

19.26 (to 4 s.f.)

3. An experimenter suggests the null hypothesis, 'The water contains varying amounts of a strongly-coloured dye.' Which of the following could not be used to test this hypothesis?

Using a spectrometer, to assess the optical absorbance Abs

Using a viscometer to assess the viscosity

Using a titrimetric test with a complexing agent, and assessing the titres

Removing the water and weighing the samples

4. The Nernst equation is

E_{O, R} = E_{O, R}^{o} + \frac{R T}{n F} \ln (\frac{[O]}{[R]})

.
How many degrees of freedom DF does this equation imply?

4

5

2.5

3

5. Consider the following data, which relate to amounts of a banned insecticide in food. 22.1, 22.1, 22.3, 22.4, 22.5, 23.6, 23.7, and 23.8 ppm. What is the variance of these data?

(to 4 s.f.)

3.55 x 10⁻¹⁵(to 4 s.f.)

63.02 (to 4 s.f.)

0.4919 (to 4 s.f.)

6. When comparing the standard deviation and the variance of a data set, which of the following statements is not correct?

Variance is better than standard deviation when developing a theory.

Standard deviation is more useful to the chemical analyst than the variance.

Standard deviation is good for interpreting and reporting.

Modern software is good at calculating both the standard deviation and the variance.

7. Concerning a simple t-test: which of the following statements is NOT true?

We retain the null hypothesis if the calculated value of t is greater than t_critical.

The value of t depends only on the sample mean

X

and sample size n.

We retain the null hypothesis if the calculated value of t is less than t_critical.

The value of t is a constant, so its interpretation does not depend on the chosen significance levels.

8. The Einstein equation is E = mc².
How many degrees of freedom DF does this equation imply?

1

2

3

4.2

9. A chemist suggests the null hypothesis, 'A reaction goes to completion.' Which alternative hypothesis allows us to reject it?

At the beginning of the reaction, we can find no product.

At a point exactly half-way between the start and end of the reaction, a spectroscopic technique shows the mixture contains both reactant and product.

The rate of reaction depends on the temperature.

After the reaction stops, a titration shows that the reaction mixture contains both reactant and product.

10. A chemist compiles a great many data sets.
Which of the following sets represents nominal data?

10, 12, 14, 16, 18, and 20

First = 14.2; second = 14.4; third = 14.6; and fourth = 14.9

Date, make of reagent, grid reference

First, second, …, fifth readings

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