A student titrates an unknown amount of potassium hydrogen phthalate (KHC8H4O4, often abbreviated KHP) with 20.46 mL of a 0.1000-M NaOH solution. KHP (molar mass 5 204.22 g / mol) has one acidic hydrogen. What mass of KHP was titrated (reacted completely) by the sodium hydroxide solution

The mass of KHP present in the solution is 0.42 g.

Explanation:

This is the titration reaction:

KHP-H + NaOH → KHP-Na + H₂O

From the equation, we know that 1 mol KHP reacts with 1 mol NaOH (because KHP has one acidic hydrogen). If we know how many moles of NaOH were used to complete the reaction, we can find how many moles of KHP were present.

The moles of NaOH used can be calculated using the data provided by the problem:

moles of NaOH used = Concentration NaOH * volume of NaOH.

Molarity (M) is a concentration unit that means mol/l.

mol NaOH = 0.1000 mol/1000ml * 20.46ml = 2.046 x 10⁻³ mol

Then, since 1 mol NaOH reacts with 1 mol KHP, 2.046 x 10⁻³ mol NaOH will react with 2.046 x 10⁻³ mol KHP.

The mass of 1 mol KHP (the molar mass) is 204.22g. Then, the mass of 2.046 x 10⁻³ mol KHP will be (2.046 x 10⁻³ mol * 204.22g / 1 mol) 0.42 g