Sapling Learning Map db A solution of HNO3 is standardized by reaction with pure

Question

Sapling Learning Map db A solution of HNO3 is standardized by reaction with pure sodium carbonate 2H++ Na2CO3 2Na+ + H2O + CO2 A volume of 28.18 ± 0.05 mL of HNO3 solution was required for complete reaction with 0.9600 ± 0.0009 g of Na2COg (FM 105.988 ± 0.001). Find the molarity of the HNO3 and its absolute uncertainty. Note: Significant figures are graded for this problem. To avoid rounding errors, do not round your answers until the very end of your calculations. Number Number HNO,-0.681 | MI ± 110.002 Incorrect

Explanation / Answer

Solution- The equation is

2 HNO3 + Na2CO3 2 NaNO3 + H2O + CO2

Doing the calculation with the values which would produce the greatest molarity:
(0.9600 + 0.0009g Na2CO3) / (105.988 - 0.001 g/mol) x (2 mol HNO3 / 1 mol Na2CO3) /
(28.18- 0.05 mL HNO3) = 0.0006445 mol/mL = 0.6445 mol/L

Redoing the calculation with the values which would produce the smallest molarity:
(0.9600 - 0.0009g Na2CO3) / (105.988 + 0.001 g/mol) x (2 mol HNO3 / 1 mol Na2CO3) /
(28.18 +0.05 mL HNO3) = 0.0006411 mol/mL = 0.6411 mol/L

Find the average:
( 0.6445 + 0.6411) / 2 = 0.6428

Find half the difference:
(( 0.6445 - 0.6411)) / 2 =0.0017

So the resulting answer is:
0.643 ±0.002 mol/L HNO3

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