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SLIB quantitative chemistry homework
I. Molar Masses
Calculate the molecular mass of the following.
H2SO4
Cl2
Calcium hydroxide
Oxygen gas
CO2
Dinitrogen monoxide
NaOCl
Al2S3
II. Fraction and Percent Composition
Calculate percent composition of the following.
1. CaSO4
2. Ba(CN)2
III. Mole Calculations
1.
Calculate the mass of 1.58 moles CH4.
2.
What volume will 7.29 moles of CO2 gas occupy at STP?
3.
How many molecules are there in a 0.00583 mole sample of H2O?
4.
How many ions are in a 35.0 gram sample of NaCl?
5.
How many moles of oxygen atoms are present in 11 grams of C6H12O6?
6.
How many hydrogen atoms are in 1 mole of water?
7.
How many moles of hydrogen atoms are in 11 moles of water?
8.
How many total atoms are present in 0.1 mole of C2H4?
9.
How many total atoms are present in 36 molecules of C6H12O6?
10.
How many molecules are there in a 0.0752 mole sample of H2O?
11.
How many formula units are present in 17.0 g of Ba3(PO4)2?
12.
How many ions are present in 17.0 g of Ba3(PO4)2?
IV. Formulas
1.
A compound was analyzed and found to contain 76.57% carbon, 6.43% hydrogen, and 17.00% oxygen by
mass. Calculate the empirical formula of the compound. If the molar mass of the compound is 94.11g/mol,
what is the molecular formula of the compound?
2.
A compound was analyzed and found to contain 53.30% carbon, 11.19% hydrogen, and 35.51% oxygen by
mass. Calculate the empirical formula of the compound. If the molar mass of the compound is 90.12 g/mol,
what is the molecular formula of the compound?
3.
Menthol, the substance we can smell in mentholated cough drops, is composed of C, H, and O. A 0.1005 g
sample of menthol is combusted, producing 0.2829 g of CO2 and 0.1159 g of H2O. What is the empirical
formula for menthol?
4.
Calculate the empirical formula of a compound that is 36.8% nitrogen and 63.2% oxygen.
5.
The molecular formula of trioxane, which contains carbon, hydrogen, and oxygen, can be determined using
the data from two different experiments. In the first experiment, 17.471 g of trioxane is burned in the
apparatus shown above, and 10.477 g H2O and 25.612 g CO2 are formed. In the second experiment, the
molecular mass of trioxane is found to be 90.079.
V. Stoichiometry
1.
__C4H10 + __O2  __CO2 + __H2O
2.
__C7H6O2 + __O2  __CO2 + __H2O
3.
__P4O10 + __H2O  __H3PO4
4.
__FeS2 + __O2  __Fe2O3 + __SO2
5.
__NH3 + __O2  __NO + __H2O
6.
Several brands of antacid tablets use aluminum hydroxide to neutralize excess acid.
Al(OH)3(s) + 3 HCl(aq)  AlCl3(aq) + 3 H2O(l)
[Molar masses:
78.01
36.46
133.4
18.02]
What quantity of HCl, in grams, can a tablet with 0.750 g of Al(OH)3 consume?
7.
The reaction of methane and water is one way to prepare hydrogen:
CH4(g) + H2O(g)  CO(g) + 3 H2(g)
[Molar masses:
16.04
18.02
28.01
2.02]
If you begin with 995 g of CH4 and 2510 g of water, what is the maximum possible yield of H2?
8.
Disulfur dichloride, S2Cl2, is used to vulcanize rubber. It can be made by treating molten sulfur with gaseous
chlorine:
S8(l) + 4 Cl2(g)  4 S2Cl2(l)
[Molar masses: 256.6
70.91
135.0]
Starting with a mixture of 32.0 g of sulfur and 71.0 g of Cl2, which is the limiting reactant? What mass of
S2Cl2 (in grams) can be produced? What mass of the excess reactant remains when the limiting reactant is
consumed?
9.
Disulfur dichloride, which has a revolting smell, can be prepared by directly combining S8 and Cl2, but it can
also be made by the following reaction:
3 SCl2(l) + 4 NaF(s)  SF4(g) + S2Cl2(l) + 4 NaCl(s)
[Molar masses:
103.0
41.99
108.1
135.0
58.46]
Assume you begin with 5.23 g of SCl2 and excess NaF. What is the theoretical yield of S2Cl2? If only 1.19 g
of S2Cl2 is obtained, what is the percent yield of the compound?
VI. Gas Laws
1.
The pressure of 4.0 L of an ideal gas in a flexible container is decreased to one-third of its original pressure
and its absolute temperature is decreased by one-half. The volume then is
a) 1.0 L b) 4.0 L c) 6.0 L d) 8.0 L e) 24 L
2.
A given mass of gas in a rigid container is heated from 100 C to 300 C. Which of the following best
describes what will happen to the pressure of the gas? The pressure will…
a) decrease by a factor of three.
b) increase by a factor of three.
c) increase by a factor less than three.
d) decrease by a factor greater than three.
3.
As the average kinetic energy of the molecules of a sample increases, the temperature of the sample
a) decreases
c) remains the same
b) increases
4.
If a gas that is confined in a rigid container is heated, the pressure of the gas will…
a) increase
c) remain the same
b) decrease
5.
If a gas has a pressure of 2.0 atm, which one of the following equations will express its pressure after...
•
the number of moles has been increased to three times the original amount,
•
the absolute temperature (K) has been reduced to half, and
•
the volume has been tripled?
1 2 4
P2 = 2.0 atm x 3 x 1 x 1
3 1 1
P2 = 2.0 atm x 1 x 2 x 3
3 2 1
P2 = 2.0 atm x x x
1 1 3
1 1 3
P2 = 2.0 atm x 3 x x 1
4
a)
b)
c)
d)
6.
Consider the following changes imposed upon a sample of gas, assuming the variables not mentioned
remain constant:
a. What happens to the pressure if the temperature in K is doubled?
b. What happens to the volume if the pressure is tripled?
c. What happens to the volume if the temperature decreases from 300K to 200K?
d. What happens to the temperature if one-half of the gas is removed?
e. What happens to the pressure if volume decreases from 4 Liters to 2 Liters and the temperature
increases from 25C to 323C
7.
A 31.0 mL sample of gas is collected at a temperature of 37 °C and pressure of 720 mmHg. What is its
volume at 17 °C and 580 mmHg.
8.
A 1.25 Liter sample of a diatomic gas, measured at STP, has a mass of 3.96 grams. What is the identity of the
gas?
9.
What is the volume of 6 moles of helium gas at 0.34 atm pressure and 33C? What is the density of the
helium gas under these conditions?
VII. Molarity
1.
Assume you dissolve 2.56 g of malic acid, C4H6O5,(mm =134.10) in 0.5 L water. Calculate the molarity.
2.
If 6.73 g of Na2CO3 (mm=105.99) is dissolved in enough water to make 250. mL of solution, what is the
molarity of the sodium carbonate?
3.
What is the mass, in grams, of solute in 250. mL of a 0.0125 M solution of KMnO4 (mm=158.04)?
4.
What volume of 0.123 M NaOH, in milliliters, contains 25.0 g of NaOH (mm=40.00)
5.
For each solution, identify the ions that exist in aqueous solution & specify the concentration of each.
a)
0.25 M (NH4)2SO4
b)
0.056 M HNO3
c)
0.123 M Na2CO3
d)
0.00124 M KClO4
6.
What volume of 0.125 M HNO3, in milliliters, is required to react completely with 1.30 g of Ba(OH)2?
2 HNO3(aq) + Ba(OH)2(s)  Ba(NO3)2(aq) + 2 H2O(l)
mm=171.36
7.
Given the equation: Al2O3(s) + 6 HCl(aq)  3 H2O(l) + 2 AlCl3(aq)
What volume of 0.250 M HCl is needed to completely react with 25.0 grams Al2O3 (mm =101.96).