EXPERIMENT 100 PRE-LABORATORY QUESTIONS SIANDARDIEATION OF A SOOIM HYDRORDE SOLU

Question

EXPERIMENT 100 PRE-LABORATORY QUESTIONS SIANDARDIEATION OF A SOOIM HYDRORDE SOLUTION NAME DATE 1. What is the purpose of this experiment? A sample of KHP has a mass of 2.345 g is used for a titration, how many moles of KHP is this sample? 3. How many moles of NaOH would be needed to reach the endpoint of this titration with sample of KHP from the previous question? 4. If the initial volume of the NaOH in the burette was 0.50 mL and the final volume is shown to the right, what is the volume of NaOH used in this titration? 5. What is the concentration of the NaOH solution used in this titration? EXPERIMENT 10 153

Explanation / Answer

Ans 1) From this experiment we determine the (concentration) molarity of NaOH by using KHP

Ans 2) moles of KHP =given mass / molar mass

Molar mass of KHP =204.22 g/mol (from literature)

Given mass of KHP =2.345 g

Moles of KHP =2.345 /204.22 =0.01148 moles

Moles of KHP =0.01148 moles

Ans 3) At the end point of the reaction

moles of KHP = Moles of NaOH

So moles of NaOH = 0.01148 moles

Ans 4) Initial volume = 0.5 mL and from figure we have final volume =18.8 mL

Total volume of NaOH required to reach end point =final volume – Initial volume = 18.8 -0.5 = 18.3 mL

Total volume of NaOH required to reach end point = 18.3 mL

5) So from ans 3 we have moles of NaOH =0.01148 moles &

volume =18.3 mL i.e. (=18.3 / 1000 =0.0183L)

Concentration of NaOH in molar = number of solute / volume in liter of solution

Concentration of NaOH in molar = 0.01148 / 0.0183=0.6274 M

So molarity of NaOH =0.6274 M

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