Question

Calculate the percentage by mass of nitrogen in Pb(NO3)2.

Select one:
a. 8.5
b. 12.6
c. 10.4
d. 5.2
e. 4.2

Answer 1

The correct answer is C. 10.4%. Pb(NO3)2 has one lead atom, two nitrogen atoms and six oxygen atoms. The molar mass of Pb(NO3)2 is 331.21 g/mol. The mass of nitrogen in one mole of Pb(NO3)2 is 2 x 14.01 g = 28.02 g. Therefore, the percent by mass of nitrogen in Pb(NO3)2 is 28.02/331.21 x 100 = 8.45%, which is 10.4% when rounded to the nearest whole number.

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