CP Chapter 10 Problems 2013-2014-answer key
DO THESE ON A SEPARATE SHEET OF PAPER THAN YOUR BOOK WORK!!!
Moles to particles
1.
2.
3.
4.
5.
The SI unit to measure the amount of a substance
How is a mole similar to a dozen? It is a specific amount of representative particles
How many particles in a mole? 6.02 x 1023 representative particles
What is another name for 6.02 x 1023? Avogadro’s number
What is a mole in chemistry?
What is the particle called for :
8.
atoms
b. an ionic compound = formula units & ions
c. a covalent compound = molecules
Explain why chemists use the mole. The numbers would be extremely large if they didn’t
24
Determine the number of atoms in 3.50 mol of Zn. 2.11x10
atoms Zn
24
Calculate the number of molecules in 12.5 mol of H2O. 7.53x10
molecules H2O
9.
Given 4.25 mol AgNO3 determine the number of formula units.
a. an element =
6.
7.
Particles to moles
How many moles are contained in each of the following?
11.2 moles Al
10.
6.75 x 1024 atoms Al
11.
1.75x 1024 molecules of CO2
12.
2.91 moles CO2
2.58 x 1023 formula units of ZnCl2 0.429 moles ZnCl2
Mole to mass (atom)
Determine the mass in grams of each of the following
13.
14.
15.
16.
150 g Al
46.6 mol Si 1310 g Si
3.49 mol Co 206 g Co
5.45 mol Zn 356 g Zn
5.57 mol Al
Mass to mole (atom)
Calculate the number of moles in each of the following
17.
25.5 g Ag
18.
300.0 g S
19.
125 g Zn
20.
1.00 kg Fe
0.236 mol Ag
9.355 mol S
1.91 mol Zn
17.9 mol Fe
Mass to atoms
How many atoms are in each of the following samples.
21.
22.
23.
24.
5.51x1024 atoms Li
21
0.530 g Pb 1.54x10 atoms Pb
22
12.5 g Hg 3.75x10
atoms Hg
24
47.6 g Si 1.02x10
atoms Si
63.5 g Li
Atoms to mass
What is the mass of each of the following samples.
25.
26.
27.
2440 g Bi
2.00 x 1024 atoms Mn 183 g Mn
6.40 x 1022 atoms He 0.425 g He
7.02 x 1024 atoms Bi
2.56x1024 Formula units Ag NO3
3.50 x 1015 atoms N 8.15x10
Mole relationship to chemical formula
28.
-8
gN
15.0 moles Cl- ions
29.
Determine the number of moles of chlorine ions present in 7.50 mol of ZnCl2
30.
Determine the number of moles of sulfate ions present in 2.00 mol of Fe2(SO4)3
31.
6.00moles (SO4)2- ions
How many moles of oxygen atoms are present in 4.00 mol of diphosphorus pentoxide. 20.0 moles O atoms
32.
Calculate the number of moles of hydrogen atoms in 12.5 mol of water.
25.0 moles H atoms
Molar mass
Determine the molar mass of each of the following ionic compounds
33.
34.
35.
36.
37.
The mass in grams of one mole of any pure substance
What is the unit for molar mass? g/mol
NaOH 40.00 g
CaCl2 110.98 g
(NH4)3PO4 149.12 g
What is the definition of molar mass?
Mole to mass of a compound
221 g
38.
What is the mass of 2.25 mol of H2SO4?
39.
What is the mass of 4.55x 10–2 moles if ZnCl2?
40.
How many grams are in 2.3 mol of calcium phosphate?
6.20 g
Ca3(PO4)2=310.18g/mol, 713.41g
Determine the number of moles present in each of the following.
41.
42.
43.
0.0352 mol
38.0 g HCl 1.04 mol
52.0 g Fe2O3 0.326 mol
3.50 g Zn(OH)2
Mass to moles to particles
A sample of Ag2CrO4 has a mass of 15.8 g
44.
45.
46.
5.73x1022 Ag+ ions
22
How many CrO42- ions are present 2.87x10
CrO42- ions
+
How many Ag ions are present
What is the mass in grams of one formula unit of silver chromate?
A sample of C2H5OH has a mass of 35.6 g
47.
48.
49.
5.51x10-22 g Ag2CrO4
9.30x1023 C atoms
24
How many hydrogen atoms are present? 2.79x10
H atoms
23
How many oxygen atoms are present? 4.65x10 O atoms
How many carbon atoms does the sample contain?
CP Practice Problems Part 2
Determine the percent by mass of each element.
1.
Calculate the percent composition of sodium sulfate. 32.37% Na, 22.58% S, 45.05% O
2.
Which has the larger percent by mass of sulfur H2SO3 or H2S2O8? H2SO3
3.
4.
What is the percent composition of phosphoric acid (H3PO4) 3.09% H, 31.60% P, 65.31% O
What is the percent composition of magnesium phosphate, Mg3(PO4)2? 27.74% Mg, 23.56% P, 48.69% O
Empirical formula
5.
Define empirical formula. A formula with the smallest whole # ratio for the subscripts.
Which compounds do not represent an empirical formula? – C2H3O, C6H12O6, CH2O, C2H6. C6H12O6, C2H6
6.
7.
8.
9.
10.
What is the empirical formula of a compound that contains 11.19% H, and 88.79% O? H2O
A blue solid is found to contain 36.84% nitrogen and 63.16% oxygen. What is the empirical formula for this solid? N2O3
Determine the empirical formula for a compound that contains 35.98% aluminum and 64.02% sulfur Al2S3
Propane Determine the empirical formula for a compound that contains 56.68% potassium, 8.68% carbon and 34.73% oxygen. K2C 03
Calculating Empirical Formula from Mass Data
11.
When an oxide of potassium is decomposed, 19.55 g K and 4.00g O are obtained. What is the empirical formula of the
compound? e.f.= K2 0
12.
Analysis of a compound yields 174.86 g Fe and 75.14 g O. Determine the empirical formula. e.f.= Fe2 03
Molecular Formula
13.
Define molecular formula. A formula that specifies the actual number of atoms of each element in one molecule or
formula unit of a substance.
14.
What is the difference between an empirical and molecular formula? Molecular formula is a multiple of an empirical formula.
Sometimes that multiple is 1, so the e.f.= m.f.
15.
If the molar mass of a compound is 180.18, what is the molecular formula for the compound is its empirical formula is CH2O?
E.F=CH2O M.F.= C6H12O6
16.
Analysis of a fluid indicates a chemical composition of 65.45% C, 5.45% H, and 29.09% O.
The molar mass is found to be 110.0 g/mol. Determine the molecular formula. E.F=C3H3O M.F.= C6H6O2
17.
A liquid is composed of 46.68% nitrogen and 53.32 % oxygen and has a molar mass of 60.01 g/mol.
What is the molecular formula? E.F.= NO
18.
M.F. = N2O2
A compound contains 26.68% C 2.24% H and 71.08%O and has a molar mass of 90.04 g/mol. E.F=CHO2 M.F.= C2H2O4
Formula of a Hydrate
19.
A hydrate of magnesium sulfate has a mass of 13.52 g. This sample is heated until no water remains. The MgSO4 anhydrate has
a mass of 6.60 g. Find the formula and name of the hydrate. MgSO4 · 7 H2O, magnesium sulfate heptahydrate
20.
A sample of copper (II) sulfate hydrate has a mass of 3.97 g. After heating, the CuSO4 that remains has a mass of 2.54 g.
Determine the correct formula and name of the hydrate. CuSO4 · 5 H2O, copper (II) sulfate pentahydrate
21.
When 5.00 g of FeCl3 · xH2O are heated, 2.00 g of H2O are driven off. Find the chemical formula and the name of the hydrate.
FeCl3 · 6 H2O, iron (III) chloride hexahydrate
22.
A hydrate is determined to be 76.9% CaSO3 and 23.1 %H2O. Find the chemical formula and the name for this hydrate. (*Hint
– assume that there are 100g total of the hydrate.) CaSO3 · 2 H2O, calcium sulfite dihydrate
23.
A hydrate is determined to be 56.14% ZnSO4 and 43.86%H2O. Find the chemical formula and the name for this hydrate.
(*Hint – assume that there are 100g total of the hydrate.) ZnSO4 · 7 H2O, zinc sulfate heptahydrate
24.
A sample of the hydrate of Na2CO3 has a mass of 8.80 g. It loses 1.28 g when heated. Find the formula and the name of the
hydrate. Na2CO3 · 1 H2O, sodium carbonate monohydrate
25.
A 16.4 g sample of hydrated CaSO4 is heated until all the water is driven off. The CaSO4 that remains has a mass of 13.0 g.
Find the formula and the chemical name of the hydrate. CaSO4 · 2 H2O, calcium sulfate dihydrate
26.
When 7.07 g of Pb(C2H3O2)2 · xH2O are heated, 1.01 g of H2O are driven off. Find the chemical formula and the name of the
hydrate. Pb(C2H3O2)2 · 3 H2O, lead (II) acetate trihydrate
27.
A hydrate is determined to be 45.43% water and 54.57% CoCl2. Find the chemical formula and name for this hydrate. (*Hintassume that there are 100 g total of hydrate compound.) CoCl2 · 6 H2O, cobalt (II) chloride hexahydrate
28.
A hydrate is determined to be 48.83% MgSO4 and 51.17% water. Find the chemical formula and name for this hydrate. MgSO4
· 7 H2O, magnesium sulfate heptahydrate
19.
MgSO4 · 7 H2O, magnesium sulfate heptahydrate
20.
CuSO4 · 5 H2O, copper (II) sulfate pentahydrate
21.
FeCl3 · 6 H2O, iron (III) chloride hexahydrate
22.
CaSO3 · 2 H2O, calcium sulfite dehydrate
23.
ZnSO4 · 7 H2O, zinc sulfate heptahydrate
24.
Na2CO3 · 1 H2O, sodium carbonate monohydrate
25.
CaSO4 · 2 H2O, calcium sulfate dehydrate
26.
Pb(C2H3O2)2 · 3 H2O, lead (II) acetate trihydrate
27.
6 H2O, cobalt (II) chloride hexahydrate
28.
MgSO4 · 7 H2O, magnesium sulfate heptahydrate