Chemistry
Name:___________________________
Unit 8 – More Mole Conversions
Date:_____________________
A. Dimensional Analysis or Factor Label Method
1.
A certain reference book lists the density of a substance as 142.9 ng/µL. What is the
density of the substance in kilograms per cubic centimeter?
(there are 109 nanograms in a gram and 106 microliters in a L, remember 1 mL = 1 cm3)
(answer: 1.429 x 10-7 kg/cm3)
B. Mole Roadmap
Use 6.022 x 1023 particles (f.a.i.m.)/1 mol for Avogadro’s number.
2. Calculate the mass, in kilograms, of 15.01 moles of mercury (I) iodide.
(answer: 9.831 kg)
3. Calculate the mass, in grams, of 4.56 x 1024 molecules of potassium thiosulfate (K2S2O3).
(answer: 1440 g)
4. Calculate the number of molecules in 0.0823 moles of uranyl (V) hexacyanoferrate(II).
(answer: 4.95 x 1022 molecules)
5. Calculate the number of molecules present in 88.1 grams of titanium (V) hypochlorite.
(answer: 1.74 x 1023 molecules)
6. Calculate the number of moles contained in 7.00 x 102 grams of hexyne (C6H10).
(answer: 8.52 mol)
7. Calculate the number of moles present in 7.25 x 10 25 molecules of the amino acid,
tryptophan.
(answer 120. mol)
C. Related Problems – the numbers of each element in a chemical formula is a whole number
MOLE ratio
8. Determine the percent composition by mass for copper (II) acetate.
Cu(C2H3O2)2
You can round percentages to tenths place.
35.0 % Cu
26.4 % C
3.3 % H
35.2% O
9. Analysis of the chemical reductone determined that it contains 40.91% carbon, 4.59%
hydrogen and 54.50% oxygen by mass (assume 100 g sample). Determine the empirical
formula of reductone.
(answer: C3H4O3)
10. A sample of piperazinium salt of acetic acid was found to contain 216.9 grams of carbon,
21.89 grams of hydrogen and 50.61 grams of nitrogen, and 115.6 grams of oxygen. The
molar mass of the compound was determined to b 448.43 g/mol. Determine the
empirical and molecular formulae for piperazinium acetate.
(answer: C5H6NO2 ; C20H24N4O8)
11. A sample of hydrated calcium phosphate was heated in a crucible and analyzed. The
following data were obtained: 31.20% of the crystal was water and 68.80% of the
crystal was calcium phosphite. Determine the formula of the hydrated crystal.
(answer: Ca3(PO4)2 · 8 H2O)