Chemistry:Atoms Questions

1.         Calculate the number of moles in each of the following masses:

1. 0.039g of palladium                =          3.665×10^-4 moles

1. 0.0073kg of tantalum

1. 3.37 x 10^-6 g of molybdenum              =          3.513×10^-8 moles

1. 1.06 x 10²³ atoms of tungsten

1. 3.008 x 10¹⁹ atoms of silver                =          4.997×10^-5 moles

1. 7.04g of Lead (II) Nitrate,  Pb(NO₃)₂

Molar mass =331.2 g/mol

Moles =  0.0213 moles

1. 0.00322g of stearic acid,  C₁₇H₃₅COOH

1. 5000Kg of Iron(III) Oxide, Fe₂O₃

2.         Calculate the number of atoms in each of the following:

1. 17.0 mol of germanium

1. 0.0019 mol of zirconium

1. 812g of gold                           atoms = 2.482×10²⁴

1. 2.00 x 10² mg of americium

1. 10.09 kg of neon

3.         Calculate the mass of each of the following:

1. 550 mol of aluminium

1. 7 mol of titanium

1. 0.0091 mol of retinoic acid, C₂0H₂₈O₂

1. 12.0 mol of ethylamine, C₂H₅NH₂

1. 9.96 x 10²⁶ atoms of tellurium

1. 2.94 x 10¹⁷ atoms of hafnium

4.         Calculate the number of molecules in each of the following:  moles x Avog # = molec.

1. 4.27 mol of tungsten(VI) oxide, WO₃

4.27mol x 6.02×10²³ = 2.571×10²⁴

1. 72.5 mol of toluene, C₆H₅CH₃

1. 1500 mol of hydrazine, N₂H₄

1. 285g of Iron (III) phosphate, FePO₄ First find molar mass.  Second,

Convert g of FePO4 to moles of FePO4 and then multiply moles x Avog. #  =

1. 4.6 x 10^-4g of mercury (II) acetate, Hg(C₂H₃O₂)₂

5. Calculate the number of specified atoms in each of the following:

1. Tungsten in 4.27 mol of tungsten(VI) oxide, WO₃ =          2.5705×10²⁴ atoms

1. Carbon in 72.5 mol of toluene, C₆H₅CH₃ =          3.0552×10²⁶ atoms

1. Hydrogen in 1500 mol of hydrazine, N₂H₄ =          3.612×10²⁷ atoms

1. Oxygen in 285g of Iron (III) phosphate, FePO₄

1. Hydrogen in 4.6 x 10^-4g of mercury (II) acetate, Hg(C₂H₃O₂)₂

6.         Calculate the percentage of the given element or molecule in each:

1. nitrogen in urea, NH₂CONH₂ %N=(28/60)x100=46.67%

1. sulfur in sulfuryl chloride, SO₂Cl₂ 32.18%

1. bromine in calcium bromide, CaBr₂ 79.95%

1. water in sodium chloride hexahydrate, SrCl₂.6H₂O               40.52%

1. water in beryllium nitrate trihydrate, Be(NO₃)₂.3H₂O           28.88%

7.         Cinnabar is a mineral that is mined in order to produce mercury.  Cinnabar is mercury (II) sulfide, HgS.  What mass of mercury can be obtained from 50g.

8.         A sample of Ag₂S has a mass of 62.4g.  what mass of each element could be obtained by decomposing this sample?

9.         Determine the Empirical Formula for the following:

1. 28.4% copper, 71.6% bromine                        CuBr₂

	g based on 100g sample	moles
Cu	28.4g	0.447	1
Br	71.6g	0.896	2

1. 39.0% potassium,12.0% carbon, 1.01 %  hydrogen,  48.0% oxygen.

The data was corrected

KHCO₃

1. 77.3% silver, 7.4% phosphorous, 15.3% oxygen

Ag₃PO₄

10.       Calculate the mass of the given element in each of the following:

1. Chromium in 1.00 kg sodium dichromate (Na₂Cr₂O₇)           397g

First Find % Cr in the compound    (that is % composition of Cr)

Second, multiply the % times 1000g of the Na₂Cr₂O₇.

1. Nitrogen in 85.0 mg of the amino acid lysine, C₆H₁₄N₂O₃ 16.3mg

1. Cobalt in 2.84 g of cobalt(II) acetate, Co(C₂H₃O₂)₂ 0.945g

11.       Determine the empirical formula for compounds that have the following analyses

a.         28.4% copper, 71.6% bromine                                                CuBr₂

b.         39.0% potassium, 12.0% carbon, 1.01% hydrogen, 47.9% Oxygen   KHCO₃

c.         77.3% silver, 7.4% phosphorous, 15.3% oxygen                             Ag₃PO₄

d.         0.57% hydrogen, 72.1% iodine, 27.3% oxygen                              HIO₃

12.       Determine the molecular formula of each unknown substance:

a.         Empirical formula CH₂ and experimental molar mass 28g/mol          C₂H₂

b.         Empirical formula C₂HCl and experimental molar mass 179g/mol    C₆H₃Cl₃

c.         Empirical formula C₆H₈O and experimental molar mass 290g/mol      C₁₈H₂₄O₃

13.       A 0.400g sample of a white powder contains 0.141g of potassium, 0.115g of sulfur and 0.144g of oxygen.  What is the empirical formula for the compound?