Logarithms in Chemistry H2o + H2O

H-O-H + H-O-H Two Water Molecules: OH- = hydroxide ion H O+ = Hydronium ion So how do you calculate the concentration of hydronium and hydroxide ions in water? ......with Logarithms from algebra! The equilibrium of water is the balance between the hydronium concentration and the hydroxide concentration. It's value is symbolized by KW. The equilibrium of water is defined as 10 Laura Josephson Using the properties and rules of logarithms,

you can solve logarithmic equations can be written as When two molecules of water collide, they transfer hydrogens, forming hydroxide and hydronium ions. O-H H-O-H

H 3 KW= [H+] [OH-] -14 Therefore, KW= [H+] [OH-] can be also be written as 10 = [H+] [OH-] -14 [H+] = 10 [OH-] = 10 -pH -pOH To use the equation

you must know either the pH or pOH of the solution 14 = pH + pOH Using logarithms, we can find that: pH = -1log[H+] pOH = -1log[oH-] We determined this using the information: [H+] = 10 [OH-] = 10 -pH -pOH Here's how: [H+] and [OH-] are exponential functions, while pH and pOH are logarithmic functions Using inverse functions and logarithmic properties, you can convert between each value Now let's apply this to chemistry! First find the pH of soil. x x x Now that we have the pH level of the soil, we can find the pOH, the hydroxide concentration and the hydronium concentration! 14 = pH + pOH Use this equation: Remember that the

pH of the soil was 6.5 14 = 6.5 + x x = 14 - 6.5

x = 7.5 The pOH of the soil was 7.5 Now Use the pOH to find the

hydroxide concentration. Remember that OH = 10 Now we can find the hydronium concentration. Use the following equation. -pOH -7.5 x -8 H = 10 -pH 10 = 3.1623 10 -7 x -6.5 Now we know the pH, pOH, hydroxide and

hydronium concentrations of our soil. pH = 6.5

pOH = 6.4

OH = 3.1628 10

H = 3.1623 10 x x -8 -7 10 = 3.1623 10

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# Logarithms in Chemistry

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