Chapter 33 Multiple choice questions

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. A temperature is measured as 325 ± 4 K. Calculate the signal-to-noise ratio and state whether the reading is usable.

The signal-to-noise ratio is 4:1 which means that the reading is usable. correct incorrect

The signal-to-noise ratio is 325:1 which means that the reading is usable. correct incorrect

The signal-to-noise ratio is 0.003:1 which means that the reading is too unreliable to use. correct incorrect

The signal-to-noise ratio is 81:1 which means that the reading is usable. correct incorrect

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. The time taken for a reaction is measured 20 times. The values range between 65 and 95 s in a Gaussian distribution.
How would we record the time taken and error?

Time = 65 ± 30 s correct incorrect

Time = 80 ± 15 s correct incorrect

Time = 95 ± 30 s correct incorrect

Time = 80 ± 1.5 s correct incorrect

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. Calculate the minimum error associated with using a 100 cm³ volumetric flask that is accurate to within ±0.1 cm³.

0.001 correct incorrect

0.0005 correct incorrect

0.01 correct incorrect

0.005 correct incorrect

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. 0.60g of a compound are weighed out on a balance that measures to the nearest 0.01 g.
What is the minimum error associated with this measurement?

0.016 correct incorrect

0.008 correct incorrect

0.01 correct incorrect

0.005 correct incorrect

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. In order to determine the conductivity of KCl solution at different concentrations, 50 cm³ of water is measured in a volumetric flask (innate error = 0.1 cm³), KCl solution is added to it in 2 cm³ aliquots from a burette (etched division markers every 0.1 cm³) and the conductance is measured using a meter which can measure to the nearest μS. The maximum conductance measured is 209 μS.
What is the minimum error associated with this experiment?

0.002 correct incorrect

0.025 correct incorrect

0.0006 correct incorrect

0.0024 correct incorrect

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. Select, from the list below, the uncertainty formula for a function of the form: y=a ln(bx), where a and b are constants.

${\sigma }_y=\left(\frac{{\sigma }_x}{x}\right)$ correct incorrect

${\sigma }_y=a\left(\frac{{\sigma }_x}{x}\right)$ correct incorrect

${\sigma }_y=ab\left(\frac{{\sigma }_x}{x}\right)$ correct incorrect

${\sigma }_y=yb\left(\frac{{\sigma }_x}{x}\right)$ correct incorrect

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. What is the innate error in the equilibrium constant, K, given that the temperature is constant (249 K) and the free energy, ΔG, is −3.14 ± 0.1 kJ mol^-1? (Remember that ∆G = −RT ln K.)

${\sigma }_K=-4.8\times {10}^{-5}$ correct incorrect

${\sigma }_K=-1.1\times {10}^{-5}$ correct incorrect

${\sigma }_K=-2.2\times {10}^{-4}$ correct incorrect

${\sigma }_K=-3.2\times {10}^{-2}$ correct incorrect

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. Pick the incorrect statement from the list below.

The correlation coefficient, r, relates to the scatter of data. correct incorrect

A correlation coefficient of 1 indicates a data set that all lies on a straight line. correct incorrect

A correlation coefficient of 0.95-1.00 indicates that there is a good degree of correlation between the x and y variables. correct incorrect

A correlation coefficient of 0 indicates a data set that is completely random. correct incorrect

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. The following data which relate the entropy of a vaporization of a material to the temperature have been collected.

$\begin{array}{|cccccc|}\hline T/K& 270& 290& 310& 330& 350\\ ∆S/J{K}^{-1}mo{l}^{-1}& 77.7& 77.5& 78.5& 78.9& 80.5\\ \hline\end{array}$

We want to test whether it is a suitable assumption that the heat capacity is constant in this temperature range. Therefore, we want to test how well the data fit the following equation:
$\Delta S=C_{\text{p}}\ln T+c$ . Calculate the r² value of the following data using a calculator
and comment on the fit of the data to the equation above.

r² = 0.96—highly likely to be linear correct incorrect

r² = 0.97—highly likely to be linear correct incorrect

r² = 0.95—highly likely to be linear correct incorrect

r² = 0.94—likely that the relationship is not linear correct incorrect

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. We are given the following set of data:

$\begin{array}{|cccccc|}\hline X& 1& 2& 3& 4& 5\\ Y& 2.7& 7.4& 20.1& 54.6& 148.4\\ \hline\end{array}$

Calculate the r² value of the following data, using a computer spreadsheet such as Excel^TM, and comment on whether there is a linear relationship between the x and y data given above.

r² > 0.95 and the relationship between x and y is linear. correct incorrect

r² < 0.8 and the relationship between x and y is linear. correct incorrect

0.81 < r² < 0.90 and the relationship between x and y is not linear. correct incorrect

r² < 0.80 and the relationship between x and y is not linear. correct incorrect