If acid has an H plus concentration of 1.0 x 10-4 M What is the pOH?

Answer 1

I advise you to first read this explanation for a better undestanding of pH of acid and base solutions.

If acid has an H plus concentration of 1.0 x 10-4 M What is the pOH? The answer is at the bottom of this tutorial.pH tutorial

At 4º Celsius, density of water = 1 gram per ml

One liter of water = 1000ml = 1000 grams of water

H2O = 18 grams per mole

1000 grams of water ÷ 18 grams per mole of water = 55.5 moles of water per liter

Of the 55.5 moles of water per liter, 10-7 moles of water split

2 H2O split into Hydronium ions ( H3O+1) and Hydroxide ions ( OH-1 ) as below.

2H2O(l) = H30+1 + OH-1

What is really happening is

When one water molecule picks up a positively charged hydrogen proton it momentarily becomes positively charged. The water molecule that looses the proton momentarily becomes negatively charged (the hydrogen's 1 electron remains behind). This is simulated in the animation available below:

http://web.jjay.cuny.edu/~acarpi/NSC/protexch.htm

The video has one problem!

The 2 H2O molecules exchange the proton when they collide with each other. After the collision, the H30+1 and OH-1 ions rapidly move away from the collision site. Thus the H30+1 and OH-1 ions that were formed from 2 H2O molecules do not reform into the same 2 H2O molecules at that site. Because of their rapid motion, they move away and find other H30+1 and OH-1 ions with which to unite.

The result of this proton exchange is that at any given moment 2 water molecules out of every 1 billion are split into a positively charged H3O+1 (called hydronium) ion and a negatively charge OH-1 (called hydroxide) ion.

2H2O(l) = H30+1 + OH-1

The equal sign (usually a double headed arrow)is used to indicate a state of equilibrium. Chemical equilibrium is the state in which the concentrations of the reactants and products have no net change over time This means as two H2O molecules split somewhere in the container, a H3O+1 ion and a OH- ion at a different place in the container go back together. This happens due to the water molecules moving around and coming into contact with each other due to kinetic energy.

In one liter of water 1.0 x 10-7 moles of waters split forming 1.0 x 10-7 moles of H3O+1 ions and 1.0 x 10-7 moles of OH-1 ions.

The brackets, [ ] around the H3O+1 and OH-1 in the equations below, means moles of H3O+1 ions and moles of OH-1 ions per liter of H2O. Kw in the equations below means equilibrium constant for water.

Kw = [H3O+1] * [OH-1]

Since the H3O+1 ion concentration in water = 10-7 moles per liter and the OH-1 ion concentration in water = 10-7 moles per liter,

Kw = [10-7(aq)] * [10-7(aq)], so Kw = 1.0 x 10-14

The subscript (aq), means in a water solution.

log means the exponent of 10, so -log 10-x = x

pH = -log of H3O+1 concentration; pOH = -log [OH-1 ] concentration

Since [H3O+1] = 10-7, -log H3O+1] = -log 10-7 = 7

pH = 7

pOH = -log of OH-1 concentration; pH = -log [OH-1]

Since [OH -1] = 10-7, -log [OH -1] = -log 10-7 = 7

pOH = 7

pH + pOH =14

Solution pH

For strong acids and bases such as HCl and NaOH

The letter N represents Normality. When measuring the concentration of strong acids or strong bases, Normality means moles of H3O+1 ions or moles of OH-1 ions per liter of H2O.

In 0.1 N HCl , [H3O+1] = 0.1 = 10-1, pH = 1

In 0.01 N HCl , [H3O+1] = 0.01 = 10-2, pH = 2

In 0.1 N NaOH, [OH-1] = 0.1 = 10-1, pOH = 1

In 0.01 N NaOH, [OH-1] = 0.01 = 10-2, pOH = 2

Your Question:

If acid has an H plus (H+1 ion) concentration of 1.0 x 10-4 M What is the pOH?

An H+1 ion can not exist, because it would be a Hydrogen atom without its electron. One H2O molecule attracts a Hydrogen proton off a second H2O molecule forming a H3O+1 ion; leaving the second H2O molecule as a OH-1 ion.

This is simulated in the animation available at the website below:

http://web.jjay.cuny.edu/~acarpi/NSC/protexch.htmTop of Form

Since the question is concerns a 1.0 x 10-4 M solution of [H3O+1] ions, the H3O+1 concentration, [H3O+1] = 10-4

pH = -log of H3O+1concentration; pH = -log [H3O+1]

Since [H3O +1] = 10-4, -log [H3O +1] = -log 10-4 = 4

pH = 4

Answer 2

pH = -log(1E-4) pH = 4