We need to calculate the pH of a   solution. There is one mole of  in every mole

of , therefore:

The equation with the relationship between pH and pOH is below:

We can calculate the pH by rearranging this equation:

Another way of solving this problem is shown below. The equation with the relationship between 

and  concentration is:

Rearranging this equation gives:

We can calculate the pH of this solution using the equation below:

The pH of a solution is related to the number of hydrogen ions in solutions. The equation to determine the pH of a solution is below:

Plugging the concentration given into the equation above gives:

Therefore, the pH of the solution is:

The pH of a solution is related to the number of hydrogen ions in solutions. The equation to determine the pH of a solution is below:

The above equation can be converted into the following form in order to determine the hydrogen ion concentration:

Therefore, the hydrogen ion concentration of a solution of pH 7 is:

The equation that expresses the relationship between pH and pOH is:

Plugging the pOH given into the equation above gives:

Rearranging this expression gives:

Therefore, the pH of a solution with a pOH of  is:

Since HCN is a weak acid, we must use the equilibrium equation.

Because the HCN dissociates in solution, we expect the concentrations of protons and cyanide ions to increase, while the concentration of HCN will decrease. After determining the molarity of the solution, we can set up the equation below, using X as the amount of moles that dissociate.

Because X is small, we can neglect its impact in the denominator.

Since X is the concentration of protons in the solution, we can calculate the pH by using the equation .

First, we must know what ferrous sulfate is. Ferrous refers to , and sulfate has the formula . When we combine the two together we get .

Calcium is a divatent cation and iodide is a monovalent anion, so their salt is . The ion exchange reaction is then:

The net ionic equation is derived by removing all spectator ions from the total ionic equation (in which all ions are listed). To put it another way, the net ionic equation involves only the ions that participate in a reaction which, in this case, is the precipitation of barium sulfate.

Begin by writing all aqueous compounds in their dissociated (ionic) forms.

Cancel out any ions that appear in equal quantities on both sides of the equation. In this case, we can cancel the nitrate and potassium ions.

This is our net ionic equation.

Combustion is the chemical reaction of a hydrocarbon with molecular oxygen, and it always produces carbon dioxide and water. Knowing the reactants and products, the unbalanced equation must be: 

We start by balancing the hydrogens. Since there are 10 on the left and only 2 on the right, we put a coefficient of 5 on water.

Similarly, we balance carbons by putting a 4 on the carbon dioxide.

To find the number of oxygens on the right, we multiply the 4 coefficient by the 2 subscript on O (which gets us 8 oxygens) and then add the 5 oxygens from the 5 water molecules to get a total of 13. The needed coefficient for  on the left would then have to be 13/2.

Because fractional coefficients are not allowed, we mutiply every coefficient by 2 to find our final reaction:

When we check the activity series, it is fairly easy to see that aluminum metal is more reactive than zinc metal. So, in this case, the two metals undergo a redox reaction, where the aqueous  is reduced to solid , and the solid  is oxidized to aqueous . These charges are the common oxidation states for zinc and aluminum and should be memorized.

Because  is the new species, it bonds with 3  ions. The unbalanced equation is:

We note that there are 2 chlorine atoms on the left and 3 chlorine atoms on the right. To balance, we use a 3 coefficient on the left and a 2 coefficient on the right. This gives a total of 6 chlorine atoms on eahc side.

However, now we have also increased the amounts of zinc and aluminum. We copy the necessary coefficients to balance those—2 for aluminum on the left, 3 for zinc on the right—and we are done:

In the unbalanced equation from the question, the reactant side contains two hydrogen atoms and one oxygen atom. On the product side of the equation, there are four hydrogens and two oxygen atoms. So for every oxygen atom there are two hydrogen atoms giving a ratio of  (oxygen : hydrogen). Putting a coefficient of two in front of the water molecule on the reactant side of the equation balances the equation. Therefore, there are four hydrogen and two oxygen atoms on both sides of the balanced chemical equation.