The three wide mouth flasks near the bottom of the experiment area labeled #1 th

Question

The three wide mouth flasks near the bottom of the experiment area labeled #1 through #3, will be used to perform three replicate titrations of KHP with a strong base, NaOH. The base solution is located in the burette (the device with the DISP button on it). The goal is to standardize the base using measured masses of KHP. The remaining flask, #4, will be used later. The pipette contains 5.00 mL of an HCl solution which will be titrated with the base solution. Flasks #1 through #3 each contain about 45 mL of water. The water will be used to dissolve the KHP after weighing. Each flask has a pH electrode (the small tube near the left side of the flask). This electrode will continuously transmit the pH to the monitor during the titrations, and the burette will broadcast the mL of base being added. You will observe the pH vs. mL of NaOH added plotted in real time as the burette slowly drips the NaOH into the flask. To start the titration experiment, the burette's DISP button is clicked (the button label will then change to STOP, and another click will stop the titration). When the endpoint of a titration approaches, the pH will rise sharply. After this steep increase, you may allow the titration to continue. Once you feel certain the endpoint has been passed, you can click on the burette's STOP button.

Explanation / Answer

Solution:

Given :

For trial 1 :

Mass of KHP = 0.191 g

Volume of base = 8.45 mL

For trial 2 :

Mass of KHP = 00.199 g

Volume of base = 8.89 mL

For trial 3 :

Mass of KHP   = 00.193 g

Volume of base = 8.93 mL

We know the reaction between KHP and base

HC8H4O4- (aq) + OH- (aq)--- > C8H4O42- (aq) + H2O (l)

From the reaction we observe that mole ration between KHP and base is 1:1

So number of moles of KHP and base will be equal.

Lets calculate moles of KHP for each trial and by using it we get moles of base which will further be used to calculate concentration of base.

For trial 1:

Mole of KHP

Mol KHP = Mass of KHP in g * 1 mol KHP / molar mass of KHP

= 0.191 g * 1 mol / 204.233 g

= 0.000935 mol KHP

Number of moles of KHP = Number of moles of base = 0.000935

[base]= Number of moles of base / volume of base in L

         = 0.000935 mol base / (8.45 E-3 L )

         = 0.111 M

[Base]= 0.111 M

For Trial 2

Mole of KHP

Mol KHP = Mass of KHP in g * 1 mol KHP / molar mass of KHP

= 0.199 g * 1 mol / 204.233 g

= 0.000974 mol KHP

Number of moles of KHP = Number of moles of base = 0.000974

[base]= Number of moles of base / volume of base in L

         = 0.000974 mol base / (8.89 E-3 L )

         = 0.110 M

[Base]= 0.110 M

For trial 3:

Mole of KHP

Mol KHP = Mass of KHP in g * 1 mol KHP / molar mass of KHP

= 0.193 g * 1 mol / 204.233 g

= 0.000945 mol KHP

Number of moles of KHP = Number of moles of base = 0.000945

[base]= Number of moles of base / volume of base in L

         = 0.000945 mol base / (8.89 E-3 L )

         = 0.106 M

[Base]= 0.106 M

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