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Let x and y be any real numbers:

log x = y

x = log inv (y) = 10^y

Example:

pH =13.22 = -log [H+]
log [H+] = -13.22
[H+] = inv log (-13.22) = 10^(-13.22)
[H+] = 6.0 x 10-14 M

FINDING ANTILOGARITHMS using a calculator (also called Inverse Logarithm)

Sometimes we know the logarithm (or ln) of a number and must work backwards to find the number itself. This is called finding the antilogarithm or inverse logarithm of the number. To do this using most simple scientific calculators,

  1. enter the number,
  2. press the inverse (inv) or shift button, then
  3. press the log (or ln) button. It might also be labeled the 10x (or ex) button.
  • Example 5: log x = 4.203; so, x = inverse log of 4.203 = 15958.79147..... (too many significant figures)
    There are three significant figures in the mantissa of the log, so the number has 3 significant figures. The answer to the correct number of significant figures is 1.60 x 104.
  • Example 6: log x = -15.3;
    so, x = inv log (-15.3) = 5.011872336... x 10-16 = 5 x 10-16 (1 significant figure)

Natural logarithms work in the same way:

  • Example 7: ln x = 2.56; so, x = inv ln (2.56) = 12.93581732... = 13 (2 sig. fig.)

Application to pH problems:

pH = -log (hydrogen ion concentration) = -log [H+]
  • Example 8: What is the concentration of the hydrogen ion concentration in an aqueous solution with pH = 13.22? pH = -log [H+] = 13.22
    log [H+] = -13.22
    [H+] = inv log (-13.22)
    [H+] = 6.0 x 10-14 M (2 sig. fig.)
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Q: How do you find the inverse log of a number?
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Related questions

How do you find the inverse log of a number using windows calculator?

The calculator won't do it.On the calculator, the button marked 10x gives youthe inverse log of the number in the window.


How do you find the inverse log using a TI 84 plus?

The 2nd function of the log button is the inverse log. Press 2nd log, which displays 10^( on the screen. Put a number after the opening parenthesis.


Find the inverse log of negative 3.1?

The inverse of the logarithm of a number is ten to the number, meaning that the number is the exponent. In this case, 10^-3.1 equals approximately .0007943.


Inverse log of - 0.123?

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How do you use inverse log on graphing calculator?

The inverse of a logarithmic function is an exponential function. So to find the "inverse" of the log function, you use the universal power key, unless you're finding the inverse of a natural log, then you use the e^x key.


Are inverse and power of -1 the same?

Sometimes. The inverse of y sin x is y sin-1x, the inverse of a number is one divided by the number, also called the reciprocal of the number, y x, then y-1 x-1 1/x. However, the inverse logarithm of a given number is the number whose logarithm is the given number. Log of 1000 is 3 and 1000 is inverse log 3.


How do you find the inverse natural log of a number?

If y = ln x, then ey = x, so antiloge y is simply ey.


How do you find the inverse of logbX?

b^x In general the log and the exponential are inverses.


What is the anti-log of 12.34?

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What is the inverse log of 2?

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What is shift log?

It depends on what calculator you are using. Often, shift log is inverse log, or natural log, but it could have other meanings. Please restate the question and specify the model number of the calculator.


Inverse logs on TI-83 plus?

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