Question

22. Calculate the number of moles of the following atoms or molecules: (a) 21.50 g of arsenic
(b) 66.50 g of fluorine atoms
(c) 2431 g of magnesium

(d) 15 g of chromium (III) oxide. (e) 0.0015 g of Cu(NO3)2
(f) 15.6 kg of silver chloride.
(g) 6.022x1023 molecules of N2 (h) 10 atoms of lithium.

Answer 1

(a) 21.50 g of arsenic

MW Arsenic = 74.9216

mol = mass/MW = 21.5/74.9216 = 0.286966 mol

(b) 66.50 g of fluorine atoms

MW F = 19

mol = mass/MW = 66.5/19 = 3.5 mol of F

(c) 2431 g of magnesium

MW Mg = 24.305

mol = mass/MW = 2431/24.305 = 100.02057 mol of Mg

(d) 15 g of chromium (III) oxide.

MW = 151.99

mol = masS/MW = 15/151.99 = 0.09869070 mol

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