Advance Study Assignment- Chemistry 180 Determination of Percent KHP in an Unkno

Question

Advance Study Assignment- Chemistry 180 Determination of Percent KHP in an Unknown A student titrates three samples made of potassium hydrogen phthalate (KHP) mixed with an inent material. He collects the following data, using 0.09607 M NaOH. Sample 1 Sample 2 Sample 3 Mass of sample, g 0.5684 0.5501 0.5622 Initial reading of NaOH buret, mL Final reading of NaOH buret, mL 0.87 0.41 0.43 17.16 16.98 16.94 1. For each sample, calculate the percent KHP. Include chemical equations where relevant to the calculations. Sample 3: (over) Sample 2: Sample 1: Exp. 9-Determination of % KHP in an Unknown 109

Explanation / Answer

1)

NaOH + KHP----> NaKP + H20

Sample 1:

Given that mass of Sample = 0.5684 g

Volume of NaOH = 17.16 ml – 0.87 ml

= 16.29 ml

= 0.01629 L

Moles of NaOH = Molaity * volume in L

= 0.09607 * 0.01629

= 0.00156 moles NaOH

                       

Now calculated the mole of KHP in sample as follows:

0.00156 moles NaOH* 1/1=0.00156 moles KHP

Amount of KHP = 0.00156 moles KHP * molar mass

= 0.00156 moles KHP *204.2 g/ mole

= 0.3196 g

% of KHP in sample = mass of KHP / sample mas ]*100

= 0.3196 g/ 0.5684 g]*100

= 56.22%

Sample 2:

Given that mass of Sample = 0.5501 g

Volume of NaOH = 16.98 ml – 0.41 ml

= 16.57 ml

= 0.01657 L

Moles of NaOH = Molaity * volume in L

= 0.09607 * 0.01657

= 0.00159 moles NaOH

                       

Now calculated the mole of KHP in sample as follows:

0.00159 moles NaOH* 1/1=0.00159 moles KHP

Amount of KHP = 0.00159 moles KHP * molar mass

= 0.00159 moles KHP *204.2 g/ mole

= 0.325 g

% of KHP in sample = mass of KHP / sample mas ]*100

= 0.325 g/ 0.5501 g]*100

= 59.09%

Sample 3:

Given that mass of Sample = 0.5622 g

Volume of NaOH = 16.94 ml – 0.43 ml

= 16.51 ml

= 0.01651 L

Moles of NaOH = Molaity * volume in L

= 0.09607 * 0.01651

= 0.00159 moles NaOH

                       

Now calculated the mole of KHP in sample as follows:

0.00159 moles NaOH* 1/1=0.00159 moles KHP

Amount of KHP = 0.00159 moles KHP * molar mass

= 0.00159 moles KHP *204.2 g/ mole

= 0.325 g

% of KHP in sample = mass of KHP / sample mas ]*100

= 0.325 g/ 0.5622 g]*100

= 57.81%

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