Graphing, mixture experiments

FIGURE 9.2 (a) In the synthesis of ammonia, the concentrations of N, and H, decrease with time and that of NH1 increases until they finally settle into values corresponding to a mixture in which all three are present and there is no further net change, (bi If the experiment is repeated with pure ammonia, it decomposes, and the composition settles down into a mixture of ammonia, nitrogen, and hydrogen. (The two graphs correspond to experiments at two different temperatures, and so they correspond to different equilibrium compositions.)... 

C05-0015. A molecular beam experiment of the type illustrated in Figure 5J is performed with an equimolar mixture of He and CO2. Sketch the appearance of a graph of the number of molecules reaching the detector as a function of time. 

Figure 2.26 represents an example of an ARC plot of the logarithm of the self-heat rate versus the reciprocal temperature. This graph shows the temperature at which a sample or mixture starts to decompose or react measurably, and the rate at which the sample or mixture liberates heat as a function of temperature. In the ARC experiment represented in Figure 2.26, exothermic decomposition or reaction is first observed at 80°C with a self-heat rate of 0.025°C/min. The maximum temperature reached is 142°C with a maximum self-heat rate of 6°C/min. The data must be corrected for the thermal inertia () of the system. 

A series of laboratory experiments with a pure substance (shown in Figure 2-2) will result in data for pressure, temperature, and volume. A similar series of experiments with a two-component system will result in data for additional variables. The composition of the overall mixture, the composition of the equilibrium liquid, and the composition of the equilibrium gas are all important. Therefore, in addition to plotting combinations of temperature, pressure, and volume, additional graphs with these variables plotted against composition are possible. 

In the lower graph, where the elapsed time is recorded in terms of individual drops, elements 103 and 102 would appear first if they existed in the original mixture they are shown in dotted lines to indicate their predicted positions. In actual experiments, which have not been conducted with element 102, mendelevium appears first, followed by fermium, einsteinium, and so on. 

An alternative approach is first to analyse the sample, noting the area, Ai, for the analyte. Successive standard amounts of the analyte are then added, each sample + standard mixture being analysed and the areas recorded. A graph of peak area versus concentration is drawn and the amount of analyte in the sample obtained by projection of the calibration line to intersect the abscissa as shown in Figure 2.9. This approach is conveniently illustrated by the determination of water in methanol by GC using thermal conductivity detection experiment 24, Chapter 9. 

Qualitative experiment under isothermal conditions. Inject 1 il samples of ethanol, -propanol, n-butanol, n-pentanol and t-butanol in turn onto the column followed by the 3 pi sample of a mixture of the first four. Note the sequence of elution and obtain the retention times for each alcohol. Plot a graph of logio retention times against... 

Fig. 8 TEX-PEP profiles for labeled 2-methylpentane left) and n-hexane (right) at several detection positions in an equimolar mixture of n-hexane and 2-methylpentane in silicalite-1 at a total hydrocarbon pressure of 6.6 kPa and a temperature of 433 K (note that these two graphs have been obtained from two different experiments in which one of the two hydrocarbons was labeled)...

Fig. 2.15. Graph of In (—dv/dr) versus In [H] for recombination rate data of three experiments ( , A, ) carried out under nearly identical conditions in a 1-0% H2-3-0% O2-96-0% Ar (i =0-33) mixture. Initial pressure 15 cm Hg. Mean reaction-zone temperature 1415 K. V values range between 0-55 and 0-004, and cover a period, At, of about 450 fisec. Slope of line determined by least-squares fit = 1-01 0-01 (after Getzinger and Schott ).

The compressive strength of HP-PE/carbon hybrids with different compositions is shown in Figure 1 and is in good agreement with the "rule of mixtures". At least 5 experiments were carried out for each dataprint. The error bars in the graph represent one standard deviation on either side of the mean value. 

Record the data for the distillation temperature as a function of the volume of distillate. Construct a graph for these data (see "Analysis" in Experiment 7A). Compare the graphs for simple and fractional distillations of the same mixture. Which distillation resulted in a better separation Explain. Report the approximate boiling points for the two compounds in your mixture and identify the compounds. 

An experiment is conducted in which varying amounts of solid iron are added to a fixed volume of liquid bromine. The product of the reaction is a single compound, which can be separated from the product mixture and weighed. The graph shows the relationship between the mass of iron in each trial versus the mass of the product compound. Explain why the graph has a positive slope for low masses of iron and a zero slope when the mass of iron added becomes larger. 

---