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Question: Plotting pH of a solution as a function of an initial concentration. Not able to see plot near initial concentration zero.

Question:Plotting pH of a solution as a function of an initial concentration. Not able to see plot near initial concentration zero.

zenterix 405 Maple 2022
plotting
April 26 2025
0

Today I was working on some plots involving pH, which is defined as -log_10 ([hydronium]), that is, the negative of the base 10 logarithm of the concentration of hydronium in a solution.

I reached an expression for a variable x that is a function of an initial concentration C_i.

I wanted to plot the pH given by -log_10 (0.0001+x).

Note that x(0)=0, and so for this latter plot we should have the point (0, 4).

I am not able to see any part of the plot near (0,4), as can be seen below.

plot(-log[10](0.1e-3+x))

  

x := -0.2550000000e-2+0.5000000000e-4*sqrt(2601.+(2.000000000*10^6)*C__i)

-0.2550000000e-2+0.5000000000e-4*(2601.+2000000.000*C__i)^(1/2)

 (1)

plot(-log[10](0.1e-3+x))

  

I want to see the plot being 4 at C__i = 0.

 

Note that subs({C__i = 0}, x) = 0. and evalf(subs({C__i = 0}, -log[10](0.1e-3+x))) = 4.000000000 

NULL

plot(-log[10](0.1e-3+x), C__i = 0 .. 1)

  

plot(-log[10](0.1e-3+x), C__i = 0 .. 1, view = [0 .. 1, 1 .. 4])

  

plot(-log[10](0.1e-3+x), C__i = 0 .. 1, view = [0 .. .1, 1 .. 4])

  

NULL

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