Химия на английском. Модуль 1
.pdf2.20.For the compound Cd(NO3)2 4H2O, calculate:
a)how many moles of Cd and of N are contained in 132.4 g of it;
b)how many molecules of water of hydration are in this same amount.
2.21.How many moles and grams of Fe and of S are contained in:
a)1 mol of FeS2 (pyrite);
b)exactly 1 kg of FeS2.
2.22.A certain public water supply contained 0.10 ppb (part per billion) of
chloroform, CHC13. How many molecules of CHC13 would be contained in a 0.05-mL drop of this water?
2.23.Find the number of molecules in:
a)25.0 g of H2O;
b)1.00 kg of sugar, C12H22O11;
c)1.00 microgram of NH3;
d)5.00 mL of CCl4 whose density is 1.594 g/mL.
2.24.Determine the number of molecules in:
a)50.0 g of mercury;
b)0.500 kg of glucose C6H12O6;
c)1.00 nanogram of HCl;
d)25.0 mL of benzene, C6H6, whose density is 0.879 g/mL.
2.25.Calculate the mole number of each of the following compounds:
a)15.2 g N2O3;
b)17.1 g Al2(SO4)3;
c)87.6 g CaCl2·6H2O.
2.26.Perform the following conversions:
a)8.8 g NaOH = ? mol NaOH;
b)0.05 mol Ca3(PO4)2 = ? g Ca3(PO4)2;
c)2.4x1023 H2O molecules = ? mol H2O = ? g H2O;
d)17.16 g Na2CO3·10H2O = ? mol Na2CO3·10H2O = ? Na2CO3·10H2O molecules.
2.27.These problems refer to dinitrogen pentoxide, N2O5.
a)Calculate the molar mass.
b)Find the mass of 1.25 mol N2O5.
c)How many moles of N2O5 are there in 5.4 g of compound?
d)Calculate the mass of compound that contains 0.5 mol of oxygen atom.
e)Calculate the mass of compound that contains 6.4 g of oxygen.
f)Find the mass of N combined with 32 g of oxygen.
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g)Calculate the number of N atoms in 21.6 g of N2O5.
2.28.Answer the following questions for CO2. Find:
a)its molar mass;
b)the mass of 1.25 mol of CO2;
c)the mole number in 17.6 g of compound;
d)the number of molecules in 6.6 g of CO2;
e)the mass of C combined with 0.25 mol O;
f)the mol number of O combined with 2.4 g C;
g)the number of O atoms in 35.2 g CO2;
h)the number of C atoms combined with 20 oxygen atoms.
2.29.3 mol mixture of SO2 and CO gases weighs 120 g. Find the mole number of each gas in the mixture.
2.30.What is the volume of each of the following gases at standard temperature and pressure (STP)?
a)9.25 mol SO2;
b)35.2 g CO2;
c)1.2x1024 H2 molecules.
2.31.Perform these conversions:
a)2 mol N2 = ? L (at STP);
b)6.8 g NH3 = ? L (at STP);
c)5.6 L O2 at STP = ? mol O2 = ? g O2 = ? O2 molecules;
d)4.8x1022 H2 molecules = ? mol H2 = ? L H2 = g H2.
2.32.How many atoms of nitrogen are there in 0.1 mol of Ca(NO3)2?
2.33.How many grams of Ca(NO3)2 would you need to get 1.00 gram of calcium?
2.34.What is the mass of (NH4)2SO4 that contains Avogadro's number of hydrogen
atoms?
2.35.How many N2O5 molecules are there in 1.08 g of N2O5?
2.36.How many molecules are there in 5.6 L CO2 at STP?
2.37.How many (a) grams of H2S, (b) moles of H and of S, (c) grams of H and of S,
(d)molecules of H2S are contained in 0.400 mol H2S?
2.38.Answer the following questions for P2O5 that contains 0.62 g of phosphorus.
a)Find the mole number of P2O5.
b)Find the number of molecules of P2O5.
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c)Find the mass of O in the compound.
d)Find the total number of atoms in the compound.
2.39.0.02 mol of unknown compound Y2O5 weighs 2.16 g. Calculate:
a)the molar mass of the compound;
b)the atomic mass of the element, Y;
c)the mass of a single Y atom.
2.40.0.05 mol of an unknown compound X(ClO3)2 is 15.2 g. Find the atomic mass and the mass of a single X atom.
2.41.3.42 g X2(SO4)3 contains 0.12 mol of oxygen atoms. What is the atomic mass
of X?
2.42.104.8 g of Mg3(YO4)2 contains 0.8 mol of Y. What is the atomic mass of Y?
2.43.35.7 g of Cr2(X2O4)3·6H2O contains 8.1 g H2O. What is the atomic mass of X?
2.44.10.4 g of X combine with oxygen to form 15.2 g of X2O3. What is the atomic mass of X?
2.45.When 1.92 g Y is heated with aluminum, 3 g of Al2Y3 are formed. What is the atomic mass of Y?
2.46.0.25 mol of CnH2n–2 contains 1.5 mol of H atoms. What is the molar mass of the compound?
2.47.0.5 mol compound with a general formula CnH2n+2 contains 3 mol of H. Find the molar mass of the compound.
2.48.A sample weighing 42.6 g of NX3 occupies 13.44 L at STP. Find the atomic mass of the element X.
2.49.Find the atomic mass of X in each of the following problems.
a)The mass of a single X atom is 1.5 x 10–23 g.
b)2.4 x 1023 molecules of XCl2 is 44.4 g.
c)5.6 L of XH3 at STP is 8.5 g.
d)0.4 mol PX3 and 0.6 mol PX5 weigh 367 g.
c) 3.84 g Li2SiX6·2H2O contains 0.72 g H2O.
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3.CALCULATING THE PERCENTAGE BY MASS
3.1.Calculate the percentages of oxygen and hydrogen in water H2O.
3.2.What is the percentage by mass of each element in Al2(SO4)3?
3.3.What are the percentages of boron and water in borax, Na2B4O5(OH)4·8H2O?
3.4.Calculate the percentages of elements K, Fe, C, N, and H2O in K4[Fe(CN)6]·3H2O crystals.
3.5.Which of these fertilizers has the highest percentage by mass of nitrogen?
a)Urea, N2H4CO.
b)Ammonium nitrate, NH4NO3.
c)Ammonium phosphate (NH4)3PO4.
3.6.Find the percentage by mass of nitrogen in each of the following compounds:
a) N2O; |
b) NO; |
c) NO2; |
d) NH3; |
e) N2H4; |
f) HN3. |
3.7. Find the percentage by mass of sodium and sulfur in the following sodium salts:
a) Na2SO4; |
b) Na2S2O3; |
c) Na2SO4·10H2O; |
d) Na2S2O3·5H2O. |
3.8.Determine the percentage composition of potassium carbonate (the percentage composition = the percentage by mass of each element).
3.9.Calculate the percentage composition of the following compounds:
a) Ca(CN)2; |
b) (NH4)2CO3; |
c) UO2(NO3)2·6H2O; |
d) C16H26O4N2S (penicillin). |
3.10. Find the percentage composition of the following compounds:
a) (NH4)2CrO4; |
b) PtP2O7; |
c) BiONO3·H2O; |
d) C21H29O12N7 (streptomycin). |
3.11.A sample of a compound contains 18.02 g C, 2.52 g H, 3.50 g N, 4.00 g O and
8.02g S. What is the percentage by mass of each element in the compound?
3.12.A sample having a mass of 0.924 g was decomposed into its components and found to have 0.389 g of carbon, 0.059 g of H and 0.476 g of O. Find the percentage composition of this substance.
3.13.What is the empirical formula of a compound consisting of 7.8 g of potassium,
7.1g of chlorine and 9.6 g of oxygen?
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3.14.A borane (containing only B and H) contained 88.45 % B. What is its empirical formula?
3.15.When 10.24 g of Cu is heated in an atmosphere of oxygen, 11.52 g of an oxide of copper is produced. What is the empirical formula of the oxide formed?
3.16.A 2.522 g sample of pure caffeine contains 1.248 g of carbon, 0.130 g of hydrogen, 0.728 g of nitrogen and 0.416 g of oxygen. What is the simplest formula of caffeine? If the molar mass of caffeine is 194, what is its molecular formula?
3.17.Cocaine is 67.30 % C, 6.98 % H, 21.10 % O, and 4.62 % N. What is the simplest formula of cocaine?
3.18.What is the simplest formula of the compound that shows the following analysis: 44.83 % potassium, 18.39 % sulfur, 36.78 % oxygen?
3.19.From the following analytical results (percentage by mass), determine the empirical formulas for the compounds analyzed:
a) 42.9% C, 57.1% O; |
b) 77.7% Fe, 22.3% O; |
c) 27.3% C, 72.7% O; |
d) 70.0% Fe, 30.0% O; |
e) 53.0% C, 47.0% O; |
f) 72.4% Fe, 27.6% O. |
3.20.Find the empirical formulas of the salts with the following percentage by mass:
a)40.2% K, 26.9% Cr, 32.9% O;
b)26.6% K, 35.4% Cr, 38.0% O;
c)19.3% Na, 26.8% S, 53.9% O;
d)29.1% Na, 40.5% S, 30.4% O;
e)32.4% Na, 22.6% S, 45.0% O.
3.21.Determine the empirical formula for each of the compounds:
a)21.8% Mg, 27.9% P, 50.3% O;
b)66.8% Ag, 15.9% V, 17.3% O;
c)79.3% Tl, 9.9% V, 10.8% O;
d)25.8% P, 26.7% S, 47.5% F;
e)19.2% P, 2.5% H, 78.3% I;
f)52.8% Sn, 12.4% Fe, 16.0% C, 18.8% N;
g)14.2% Ni, 61.3% I, 20.2% N, 4.3% H.
3.22.A compound has the following percentage composition by mass: 58.8 % C, 9.8
%H, and the remainder is oxygen.
a)Calculate the empirical formula of the compound.
b)If 0.2 mol of the compound weighs 40.8 g, find its molecular formula.
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3.23.What are the empirical formulas of the compounds with the following composition:
a)38.71 % C, 16.13 % H, and 45.16 % N;
b)26.53 % K, 35.37 % Cr, the remainder is oxygen;
c)21.8 % Mg, 27.8 % P, and 50.3 % O;
d)79.1 % CaSO4, 20.9 % H2O;
e)37.7 % Na, 22.95 % Si, the remainder is oxygen.
3.24.A given compound consists of 6.02x1022 atoms of carbon, 1.806x1023 atoms of hydrogen and 6.02x1022 atoms of oxygen. What is its simplest formula?
3.25.The analysis of a compound showed that it contained 7.2 g carbon, 1.2 mol hydrogen, and 3.6x1023 atoms of oxygen. What is the molecular formula of the compound, if its molar mass is 180 g/mol?
3.26.Pyrex glass typically contains 12.9 % B2O3, 2.2 % Al2O3, 3.8% Na2O, 0.4 % K2O, and 80.7 % SiO2. What is the ratio of silicon to boron atoms in the glass?
3.27.Weighed samples of the following hydrates are heated to drive off the water, and then the cooled residues are weighed. From the data given, find the formulas of the hydrates:
a)0.695 g of CuSO4 xH2O gave a residue of 0.445 g;
b)0.573 g of Hg(NO3)2 xH2O gave a residue of 0.558 g;
c)1.205 g of Pb(C2H3O2)2 xH2O gave a residue of 1.032 g;
d)0.809 g of CoCl2 xH2O gave a residue of 0.442 g;
e)2.515 g of CaSO4 xH2O gave a residue of 1.990 g;
f)0.520 g of NiSO4 xH2O gave a residue of 0.306 g;
g)0.895 g of MnI2 xH2O gave a residue of 0.726 g;
h)0.654 g of MgSO4 xH2O gave a residue of 0.320 g;
i)1.216 g of CdSO4 xH2O gave a residue of 0.988 g;
j)0.783 g of KAl(SO4)2 xH2O gave a residue of 0.426 g.
3.28.When 3 g of Mg is burned in excess oxygen, it produces 5 g of magnesium oxide. What is the empirical formula of the oxide formed?
3.29.When 5.8 grams of silver oxide are decomposed, there remains a silver residue of 5.4 grams. Calculate the simplest formula of silver oxide.
3.30.The elemental analyses of several compounds are given below. Determine the empirical formula of each compound whose composition is shown below:
a)5.6 g Fe and 2.4 g O;
b)0.64 g S and 0.64 g O;
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c)2.82 g K, 2.56 g Cl, 4.62 g O;
d)18 g C, 1.65 g H, 2.10 g N and 2.4 g O;
e)4 g Ca, 6.02x1022 C atoms, 0.3 mol O;
f)2.78 g Co, 11.96 g I, and 4.52 g O.
3.31.A compound with a known molar mass of 28 contains 85.71% carbon and
14.29% hydrogen. Find its molecular formula.
3.32.A sample of a compound is found to contain 0.97 grams of phosphorus and
1.25grams of oxygen. If 0.02 mol of this compound weighs 5.68 g, calculate its molecular formula.
3.33.An element X forms four oxides containing 77.4, 63.2, 69.6, and 72.0 % X. If the compound with 77.4 % X is XO, what is X, and what are the empirical formulas of the other compounds?
3.34.A metal forms two different chlorides. Analysis shows one to be 51.1% Cl and the other to be 64.4% Cl by mass. What are the possible values of the atomic mass of the metal?
3.35.A metal forms two different chlorides. Analysis shows one to be 40.3% metal and the other to be 47.4% metal by mass. What are the possible values of the atomic mass of the metal?
3.36.A sample of an organic compound containing C, H, and O, which weighs
12.13mg, gives 30.6 mg of CO2 and 5.36 mg of H2O in combustion. The amount of oxygen in the original samples is obtained by difference. Determine the empirical formula of this compound.
3.37.An organic compound containing C, H, O, and S is subjected to two analytical
procedures. When a 9.33 mg sample is burned, it gives 19.50 mg of CO2 and 3.99 mg of H2O. A separate 11.05 mg sample is fused with Na2O2, and the resulting sulfate is precipitated as BaSO4, which (when washed and dried) weighs 20.4 mg. The amount of oxygen in the original sample is obtained by difference. Determine the empirical formula of this compound.
3.38.A 5.135 g sample of impure limestone (CaCO3) yields 2.050 g of CO2 (which was absorbed in a soda-lime tube) when treated with an excess of acid. Assuming the
limestone is the only component that would yield CO2, calculate the percentage purity of the limestone sample.
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4.CONCENTRATION OF SOLUTIONS
4.1.A salt-water solution is prepared by dissolving 20 g NaCl in 230 g of water. What is the percentage by mass of salt in the solution?
4.2.Calculate the percentage by mass of solute in a solution prepared by dissolving 20 g sugar in 60 g of water.
4.3.Suppose that you have 160 g of a solution that is 20% sugar by mass. Calculate the percentage concentration of the new solution resulting after:
a)it is mixed with 40 g of water;
b)32 g of water is evaporated from the original solution;
c)it is mixed with 40 g of sugar;
d)it is mixed with 40 g water and 40 g of sugar;
e)it is mixed with 840 g of a solution containing 5 % sugar.
4.4.Calculate the amount (g) of NaOH in 800 g solution that is 20 % NaOH by
mass.
4.5.Calculate the percentage concentration of the solution resulted by mixing 150 g solution that is 20% sugar by mass, 50 g solution that is 30 % sugar by mass, 85 g water and 15 g of sugar.
4.6.How much NaCl must be added to 150 g of 10 % NaCl solution so that the percentage of NaCl in the resulting solution is 20 %.
4.7.Calculate the masses of 20% and 40% sugar solutions that must be mixed to obtain 400 g of solution containing 25 % sugar by mass.
4.8.Concentrated nitric acid solution has density of 1.42 g/mL and contains 72%
HNO3 by mass. How many grams of HNO3 are there in 500 mL of this concentrated solution?
4.9.A student needs 109.5 g of HCl for a reaction. What volume of concentrated hydrochloric acid solution with a density of 1.2 g/mL and containing 36.5 % HCl by mass contains 109.5 g of HCl?
4.10.Describe how to prepare 500 mL of 1.5 M Na2SO4 solution.
4.11.30 g NaOH is dissolved in enough water to form 600 mL of solution. What is the molarity of the solution?
4.12.11.2 liters of NH3 gas measured at STP is dissolved in water to prepare 5 liters of solution. Calculate the molarity of the solution.
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4.13.Calculate the molarity of the following solutions:
a)5 L solution containing 2 mol BaCl2;
b)250 mL solution containing 7 g of KOH;
c)500 mL solution containing 6.02x1022 NH3 molecules;
d)500 mL solution containing 28.75 mL C2H5OH (d = 0.8 g/mL);
e)600 mL solution containing 6.72 L HCl measured at STP;
f)1250 mL solution containing 42.5 g of NaNO3 sample that is 80% pure.
4.14.How many grams of Fe(NO3)2 are required to make 400 mL of a solution with concentration 0.5 M Fe(NO3)2?
4.15.How many liters of 3 M NaOH solution can be prepared with 360g NaOH?
4.16.Describe how to prepare 0.2000 M CuSO4, starting with solid CuSO4 5H2O.
4.17.Tell how you would prepare each of the following solutions:
a)3.00 liters of 0.750 M NaCl from solid NaCl;
b)55.0 mL of 2.00 M ZnSO4 from solid ZnSO4 7H2O;
c)180 mL of 0.100 M Ba(NO3)2 from solid Ba(NO3)2;
d)12 liters of 6.0 M KOH from solid KOH;
e)730 mL of 0.0700 M Fe(NO3)3 from solid Fe(NO3)3 9H2O.
4.18.Tell how you would prepare each of the following solutions:
a)125 mL of 0.62 M NH4Cl from solid NH4Cl;
b)2.75 liters of 1.72 M Ni(NO3)2 from solid Ni(NO3)2 6H2O;
c)65.0 mL of 0.25 M Al(NO3)3 from solid Al(NO3)3 9H2O;
d)230 mL of 0.460 M LiOH from solid LiOH;
e)7.57 liters of 1.10 M KCr(SO4)2 from solid KCr(SO4)2 12H2O.
4.19.500 mL of water are added to 300 mL of 0.4 M H2SO4 solution. Find the molarity of the resulting solution.
4.20.100 mL of 6 M HCl solution is diluted to 600 mL. What is the molar concentration of the final solution?
4.21.What volume of water must be added to 200 mL of 3 M BaCl2 solution to obtain 1 M solution?
4.22.How many mL of water must be evaporated from 500 mL of 0.3M NaCl solution so that the concentration of NaCl becomes 0.5 M?
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4.23.Describe how you would prepare 2 L of 0.7 M HNO3 solution, starting with a concentrated HNO3 solution that has a density of 1.4 g/mL and contains 63 % HNO3 by mass.
4.24.Commercial concentrated sulfuric acid is labeled as being 96.0% H2SO4 by mass and having a density of 1.84 g/mL. Calculate the molarity of this solution.
4.25.The density of a 3.68 M sodium thiosulfate solution is 1.269 g/mL. Find the percentage of Na2S2O3 by mass.
4.26.The density of a 1.660 M Na2Cr2O7 solution is 1.244 g/mL.
a)Find the percentage of Na2Cr2O7 by mass.
b)If 1.50 liters of water are added to 1.0 liter of this solution, what is the percentage by mass of Na2Cr2O7 in the new solution?
4.27.The density of a 2.04 M Cd(NO3)2 solution is 1.382 g/mL. If 500 mL of water is added to 750 mL of this solution, what will be the percentage by mass of Cd(NO3)2 in the new solution?
4.28.How many mL of 0.5 M H2SO4 solution can be prepared from 20 mL of 2.5 M H2SO4 solution?
4.29.A 300 mL of 0.2 M HNO3 solution is added to 200 mL of 0.15 M HNO3 solution. Calculate the molarity of the resulting solution.
4.25.400 mL of 0.6 M KCl solution is added to 600 mL of 0.2 M KCl solution. What is the molarity of the final solution?
4.26.If 500 mL of 3.00 M H2SO4 is added to 1.50 liters of 0.500 M H2SO4, what is the resulting concentration?
4.27.What volumes of 2 M and 6 M solutions of HCl should be mixed to prepare 500 mL of a 3 M solution? Disregard the change in the volume in mixing.
4.28.What volumes of 4 M and 6 M KNO3 solutions should be mixed to obtain a 500 mL of 4.8 M KNO3 solution?
4.29.3.1 g MgX2 is used to prepare 500 mL of 0.1 M MgX2 solution. What is the atomic mass of X?
4.30.19.36 g of X(NO3)3 is used in the preparation of 400 mL of 0.2 M solution. Calculate the atomic mass of X.
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