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h watch TV an x R h Ki la x Indiana Sta x wwwsapling x YC Use A Sprea x C www.sap inglearning.com mod Vibis/view.php?id 3224075 /ibiscm 2/20/2017 12:00 PM N41.8/10o Gradebook Attempts Score Print Calculator Periodic Table Question 11 of 11 Sapling Learning A solution of HNO3 is standardized by reaction with pure sodium carbonate. 2H Nas CO. Na H,CO CO, A volume of 26.46 t 0.06 mL of HNO3 s was required for complete reaction with 0.9439 t 0.0008 g of olution Nazcoa, (FM 105.988 t 0.001). Find the molal of the HNOs and its absolute uncertainty. rity Note: Significant figures s are graded for this problem. To avoid rou ding errors, do not M M round your answers until the very end of HNO your calculations. A Previous Give Up 8 View Solution Check Answer Next Exit Sapling Learning Inc. about us careers partners privacy policy terms of use contact us help Assignment Information Available From: 2/10/2017 10:00 AM 2/20/2017 12:00 PM Due Date: Points Possi ble 00 Grade Category: Defa Description Policies: SFW Custom You can check your answers. You can view solutions when you complete or give up on any question. You can keep trying to answer each question until you get it right or give up. You lose 10% of the points available to each answer in your question for each incorrect attempt at that answer eTextbook O Help With This Topic O Web Help & Videos O Technical Support and Bug Reports 7:13 AM a

Explanation / Answer

Ans. Number of moles of Na2CO3 is solid sample = Mass/ Molar mass

                                                = (0.9439 ±0.0008 g) / (105.9887 g mol-1)

                                                = [(0.9439 / 105.9887) ±0.0008] mol

                                                = 0.0089 ±0.0008 mol

According to the stoichiometry of balanced reaction, the number of moles of HNO3 (monoprotic acid) required to neutralize Na2CO3 is twice the number of moles of Na2CO3.

So, number of moles of HNO3 required for neutralization = 2 x moles of Na2CO3

                                                                = 2 x (0.0089 ± 0.0008 mol)

                                                = 0.0178 ± 0.0008 mol

Now,

            Number of moles of HNO3 = Molarity x Volume (in L)

            Or, (0.0178 ± 0.0008 mol) = M x (0.02646 ± 0.0006) L

            Or, M = (0.0178 ± 0.0008 mol) / (0.02646 ± 0.06) L

            Or, M = (0.0178 / 0.02646) ± (0.0008 + 0.06) mol/ L

            Or, M = (0.6727 ± 0.0608) mol/ L = (0.6727 ± 0.0608) M

The result obtained is in from of “Actual value ± Absolute uncertainty” unit.

Hence, molarity = 0.6727 M

Absolute uncertainty = 0.0608 M

Rule for calculating uncertainty in division:

(A ± DA) unit / (B ± DB) unit = [ (A/ B) ± (DA + DB)] unit

                                                Or,               = (A/ B) unit ± (DA + DB)] unit

The same holds true for multiplication, addition, subtraction except that the sign of division is replaced by their respective sign. Note that uncertainty is added up in the very same way.

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