Question

A titration is performed on a 25.0 mL sample of calcium hydroxide. A volume of

46.0 mL of a 0.15 M solution of nitric acid is used to reach to the end point.
Calculate the concentration of the calcium hydroxide

Answer 1

`\boxed {\boxed {\sf 0.28 \ M}}`

Step-by-step explanation:

Titration is a method used to determine the concentration of a substance. The formula for this is:

`M_AV_A= M_BV_B`

Where M is the molarity of the acid or base and V is the volume of the acid or base.

We know that 46.0 milliliters of a 0.15 molar solution of nitric acid wereused in the titration. 25.0 milliliters of solution of calcium hydroxide of unknown molarity were also used.

`\bullet \ M_A= 0.15 \ M \\\bullet \ V_A= 46.0 \ mL\\\bullet \ V_B= 25.0 \ mL`

Substitute these known values into the formula.

`0.15 \ M * 46.0 \ mL= M_B * 25.0 \ mL`

We are solving for the molarity of the base, so we must isolate the variable
`M_B`. It is being multiplied by 25.0 milliliters. The inverse operation of multiplication is division, so we divide both sides of the equation by 25.0 mL.

`\frac {0.15 \ M * 46.0 \ mL}{25.0 \ mL}= (M_B * 25.0 \ mL)/(25.0 \ mL)`

`\frac {0.15 \ M * 46.0 \ mL}{25.0 \ mL}= M_B`

The units of milliliters (mL) cancel.

`\frac {0.15 \ M * 46.0 }{25.0}=M_B`

`\frac {6.9}{25.0 } \ M =M_B`

`0.276 \ M = M_B`

The original measurements have 2 or 3 significant figures. We always round our answer to the least number of sig figs, which is 2. For the number we calculated, that is the hundredths place. The 6 in the thousandths place tells us to round the 7 up to an 8.

`0.28 \ M \approx M_B`

The concentration of calcium hydroxide is approximately 0.28 M.