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Unformatted text preview: oking at the experimental data, it looks to me as if the boiling
point for 10 g/mol should not be less than, say, 50o C, so this is the va lue I will choose for
the minimum value for the boiling point. If it turns out that this guess is far too small or
far too large, I’ll choose a new minimum value and replot.
Choosing a Graph Orientation:
Once I have examined my experimental point ranges (both x and y axis), I’ll
choose an orientation for my graph. Since graph paper is usually longer than it is wide
(this may not be true if a space for graphing is provided), then I am free to choose if I
want the x axis to be along the width or length of the paper. The axis with the widest
range of values I will make the length of the paper. In our case, the boiling points, that is,
the “y” axis, has the greater differences between minimum and maximum values. Thus,
I’ll make this the length of the paper, and the molecular weights the width.
Setting Up the Axes:
Now look at the graph paper carefully, examining the number of divisions along
both the length and the width of the paper. The particular piece of graph paper that I
have chosen has 39 divisions along the width and 52 divisions along the length. I’ll need
a little space to draw in the axes, so I will leave 4 divisions along the bottom and 2
divisions from the right, making my effective graph paper 50x35. I’ll draw in the graph
axes now and label them. Notice that my lables include both the label title and the units
We’ll set the minimum values for the lower left-hand corner of the axes I’ve just
drawn. Now I have to choose the appropriate value for each division. This is as much an
art as anything else, but to get some idea, with 50 divisions spanning 50 to 200 o C, I
expect each division along the y axis to be about (200-50)/50, or about 3 o C for each
division. Before drawing anything, I’ll check this by hand. I notice that this will take my
scale up to 200 o C, so I will draw them in. First, I’ll draw a mark every fifth line.
Typically this can be every fifth or tenth line for ease. Then, I’ll write in the temperature
at each of these new divisions, and add “1 div = 3 o C” to the axis title.
Similarly, along the x axis, I expect each division to have a value (150-10)/35, or
4 g/mol per division. Checking this by hand, I see that it is exactly right, so, as with the y
axis, I’ll draw in the value every fifth division and add the line “1 div = 4 g/mol” to the x
axis title. Now my axes are set, and the graph will take the entire sheet of graph paper.
Plotting the Data and Drawing Experimental Lines: Dakota State University page 215 of 232 Plotting Experimental Data General Chemistry I and II Lab Manual Now I plot the points. Each point I’ll plot as carefully as possible, estimating the
distance between divisions when necessary. Each experimental point I’ll circle once
they’re plotted. You may notice that in our example, the points do not line up as nicely
as perhaps we would like. This makes the tas...
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