Practice problems
What is the % Ba in Ba(NO3)2?
% Ba = 137.33 g x 100 = 52.546%
What is the % Mg in MgO?
% Mg = 24.31 g x 100 = 60.32%
What is the % of each element in Ni3(PO4)2?
% Ni = 176.07 g x 100 = 48.105% 366.01 g %P= 61.94g x100=16.92% 366.01 g % O = 128.00 g x 100 = 34.972%
What is the % of each element in Al2(CrO4)3?
%Al= 53.96g x100=13.42% 401.96 g % Cr = 156.00 g x 100 = 38.810% 401.96 g % O = 192.00 g x 100 = 47.766
What is the % H in Ca(C2H3O2)2?
%H= 6.06g x100=3.83%
What is the % of each element in (NH4)2(SO4)?
%N = 28.02g x100 = 21.20% 132.17 g %H= 8.08g x100=6.11% 132.17 g %S= 32.07g x100=24.26% 132.17 g %O = 64.00g x100 = 48.42%
How many formula units are equal to a 0.25 g sample of chromium (III) sulfate, Cr2(SO4)3?
0.25 g Cr2(SO4)3 x 1 mol Cr2(SO4)3 x 6.02x1023 FU Cr2(SO4)3 = 3.8x1020 FU Cr2(SO4)3
How many molecules of carbon tetrachloride are equal to 0.25 moles?
0.25 mol CCl4 x 6.02x1023 molec CCl4 = 1.5x1023 molec CCl4
How many moles are equal to 3.67 x 1023 formula units of potassium permanganate?
3.67x1023 FU KMnO4 x 1 mol KMnO4 = 0.610 mol KMnO4
Ni3(PO4)2
366.01 g
How many moles are equal to 13.25 g of barium permanganate, Ba(MnO4)2?
1 mol Ba(MnO4)2 13.25g Ba(MnO4)2 x = 0.03531 mol Ba(MnO4)2 375.21 g Ba(MnO4)2
How many moles are equal to 89.23 g of calcium oxide, CaO?
1 mol CaO 89.23 g CaO x = 1.591 mol CaO 56.08 g CaO
How many moles are equal to 145 g of zinc nitrate, Zn(NO3)2?
1 mol Zn(NO3)2 145 g Zn(NO3)2 x = 0.766 mol Zn(NO3)2 189.40 g Zn(NO3)2
How many molecules are equal to 3.52 moles of oxygen difluoride?
3.52 mol OF2 x 6.02x1023 molec OF2 = 2.12x1024 molec OF2 1 mol OF2
How many moles are equal to 1.20 x 1024 atoms of sulfur?
1.20x1024 atoms S x 1 mol S = 1.99 mol S
How many moles are equal to 1.3 x 1024 atoms of aluminum?
1.3x1024 atoms Al x 1 mol Al = 2.2 mol Al
How many atoms are equal to 1.5 moles of helium?
1.5 mol He x 6.02x1023 atoms He = 9.0x1023 atoms He
How many formula units are equal to 1.8 moles of magnesium iodide?
1.8 mol MgI2 x 6.02x1023 FU MgI2 = 1.1x1024 FU MgI2
Na(ClO3)
106.44 g
How many molecules are in 13.5 g of sulfur dioxide, SO2?
13.5 g SO2 x 1 mol SO2 x 6.02x1023 molec SO2 = 1.27x1023 molec SO2
(NH4)2(SO4)
132.17 g
AlCl3
133.33 g
How many molecules are in a 189 g sample of carbon tetrabromide, CBr4?
189 g CBr4 x 1 mol CBr4 x 6.02x1023 molec CBr4 = 3.43x1023 molec CBr4
Zn(NO3)2
189.40 g
What is the mass of 2.23 x 1023 atoms of sulfur?
2.23x1023 atomsSx 1molS x32.07gS=11.9gS
How many molecules are equal to 2.25 moles of sulfur dioxide?
2.25 mol SO2 x 6.02x1023 molec SO2 = 1.35x1024 molec SO2
How many moles are equal to 2.4 x 1023 formula units of sodium chloride?
2.4x1023 FU NaCl x 1 mol NaCl = 0.40 mol NaCl
Cu2(CrO4)
243.10 g
How many grams are equal to 0.11 mole of copper(I) chromate, Cu2(CrO4)?
243.10 g Cu2(CrO4) 0.11 mol Cu2(CrO4)x 1 mol Cu (CrO4) = 27g Cu2(CrO4)
How many grams are equal to 3.46 moles of sodium sulfide, Na2S?
3.46 mol Na2S x 78.05 g Na2S 2g Na2S = 2.70x10 1 mol Na2S
Ba(MnO4)2
375.21 g
How many moles are equal to 4.15 x 1023 molecules of carbon monoxide?
4.15x1023 molec CO x 1 mol CO = 0.689 mol CO
How many formula units of silver fluoride, AgF, are equal to 42.15 g of this substance?
42.15 g AgF x 1 mol AgF x 6.02x1023 FU AgF = 2.000x1023 FU AgF
CaO
56.08 g
Na2S
78.05 g
What is the mass of 8.83 x 1023 formula units of Iron (III) oxide, Fe2O3?
8.83x1023 FU Fe2O3 x 1 mol Fe2O3 x 159.69 g Fe2O3 = 234 g FU Fe2O3
Mg(CO3)
84.32 g
What is the mass of 9.80 x 1023 formula units of zinc chlorate, Zn(ClO3)2?
9.80x1023 FU Zn(ClO3)2 x 1 mol Zn(ClO3)2 x 232.28 g Zn(ClO3)2 = 378 g Zn(ClO3)2
How many molecules are there in a 42.3 g sample of water, H2O?
= 1.41x1024 molec H2O
How much is left over of the excess reagent in moles?
For I2: 20 - 3x and x = 5 20 - 3(5) = 5 mols I2 left over
How much is your expected yield of NI3 in moles?
For NI3 +2x and x = 5 +2(5) = 10 mols NI3
What is the limiting reagent for this reaction?
N2 is the limiting reagent (5 < 6.7)
