[cambaby]

Ok, a student finds when she increases the temperature of a 550 mL air sample from
22.3 C to 29. C, the air pressure went from 1099 cm H2O to
1033 cm H20.
What is the slope of the line?
remember
p=m+b
ummm, WTF! PLease help

[mike]

I am not sure what p=m+b is.

The slope of a line generally refers to data plotted on a graph. The slope is the change in the y value over the change in the x value.

m = y2-y1/x2-x1

The equation for a straight line graph is y = mx+c (m = slope, c = intercept)

You basically have two data points in this question:

(x, y)

(pressure, temperature)

(1099, 22.3) and (1033, 29.0)

I am not sure why the pressure would go down when the sample was heated though?

[billnotgatez]

I thought that in the old days
One expressed the equation of a straight line as
Y = mX + b  where m is the slope and b is the intercept

The ideal gas law is PV = NrT and used absolute values for T
So you would not make a graph using degrees C

Also the dropping of pressure while applying heat to a gas would be counter intuitive.
Does the term “over water” imply that the volume changes?

It might be that this problem has typos and transpositions.
Textbooks are not always perfect

[mike]

The ideal gas law is PV = NrT and used absolute values for T
So you would not make a graph using degrees C

While this is true for absolute values it doesn't matter when refering to the slope of the graph as deltaT is the same in C and K.

The "slope" of this "graph" (really just the two data points) will be equal to nR/V and as V and R are constant you could work out the number of moles of gas.

[billnotgatez]

Mike – I guess you are correct about the use of C or K involving the slope. But, I think I would find it confusing when looking at the Y intercept if the Y-axis was temperature.