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3.E: Composition of Substances and Solutions- Homework
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For Chapter 3 you MUST know:
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The additional polyatomic ions: cyanide ( \(\ce{CN^-}\)), nitrite ( \(\ce{NO_2^-}\)), and sulfite ( \(\ce{SO_3^{2-}}\)).
Turn in your answers for the following questions - show your work
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For the following molecules; write the chemical formula, determine the molecular weight and determine the number of moles in exactly 1 gram.
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carbon dioxide
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iron (II) chloride
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dinitrogen pentoxide
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iron (III) sulfate
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Name the following compounds, determine the molecular weight and determine how many moles in 8.35 grams of the compound.
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KI
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CaF
2
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Cu
2
SO
4
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N
2
O
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LiOH
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Give the chemical formula (or atomic symbol), molecular (or atomic) weight, and charge for the following ions:
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sulfate
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sulfite
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nitrate
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chloride
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nitride
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acetate
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carbonate
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Calculate the number of moles in:
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45.3594 g of Ne
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0.198669 g of Ne
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Calculate the mass of:
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2.00 mole of Fe
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4.362 x 10
-5
mol of Fe
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Describe how to prepare 250 mL of 0.12 M lithium chloride solution from solid lithium chloride.
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Describe how to prepare 100 mL of 0.012 M lithium chloride solution from a 0.12 M lithium chloride solution.
The Following Questions are for your practice - Do Not Turn In. They include answers so you can check your work
3.1: Formula Mass and the Mole Concept
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What is the total mass (amu) of carbon in each of the following molecules?
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CH
4
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C
12
H
10
O
6
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(a)
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12.01 amu
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(b)
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144.12 amu
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Calculate the molecular or formula mass of each of the following:
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P
4
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H
2
O
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Ca(NO
3
)
2
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(a)
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123.896 amu
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(b)
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18.015 amu
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(c)
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164.086 amu
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Determine the molecular mass of the following compounds:
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(a)
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56.107 amu
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(b)
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54.091 amu
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Calculate the molar mass of each of the following:
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S
8
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C
5
H
12
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(a)
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256.528 g/mol
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(b)
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72.150 g mol
−1
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Determine the mass of each of the following:
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0.0146 mol KOH
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10.2 mol ethane, C
2
H
6
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(a)
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0.819 g
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(b)
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307 g
3.2: Determining Empirical and Molecular Formulas
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answer
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Mg
3
Si
2
H
3
O
8
(empirical formula), Mg
6
Si
4
H
6
O
16
(molecular formula)
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Calculate the percent composition of ammonia, NH
3
to four significant figures:
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answer
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% N = 82.24%; % H = 17.76%
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A compound of carbon and hydrogen contains 92.3% C and has a molar mass of 78.1 g/mol. What is its molecular formula?
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answer
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C
6
H
6
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Determine the empirical and molecular formula for chrysotile asbestos. Chrysotile has the following percent composition: 28.03% Mg, 21.60% Si, 1.16% H, and 49.21% O. The molar mass for chrysotile is 520.8 g/mol.
3.3: Molarity
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Determine the molarity for 0.444 mol of CoCl
2
in 0.654 L of solution
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answer
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0.679
M
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Determine the molarity for 98.0 g of phosphoric acid, H
3
PO
4
, in 1.00 L of solution
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answer
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1.00
M
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Calculate the number of moles and the mass of the solute in 2.00 L of 18.5
M
H
2
SO
4
, concentrated sulfuric acid:
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answer
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37.0 mol H
2
SO
4
; 3.63 × 10
3
g H
2
SO
4
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Calculate the molarity of 0.195 g of cholesterol, C
27
H
46
O, in 0.100 L of serum, the average concentration of cholesterol in human serum
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answer
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5.04 × 10
−3
M
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What is the molarity of the diluted solution when 1.00 L of a 0.250-
M
solution of Fe(NO
3
)
3
is diluted to a final volume of 2.00 L?
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answer
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0.125
M
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What volume of a 0.20-
M
K
2
SO
4
solution contains 57 g of K
2
SO
4
?
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answer
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1.6 L