# How do you calculate the pH of the solution made by adding 0.50 mol of #HOBr# and 0.30 mol of #KOBr# to 1.00 L of water?

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The value of Ka for #HOBr# is #2.0*10^{-9}# .

The value of Ka for

##### 1 Answer

#### Answer:

You can do it like this:

#### Explanation:

The expression for

These are equilibrium concentrations.

To find the

Because the value of

This means that the initial moles given will be a very close approximation to the equilibrium moles so we can use them in the expression.

There will be a volume change on adding these substances to water so the final volume will not now be 1 litre.

This does not matter as the volume is common to both so cancels out: