
Concept explainers
The chapter sections to review are shown in parentheses at the end of each problem.
Using the models of the molecules (black = C, white = H, yellow = S, green = Cl), determine each of the following for models of compounds 1 and 2: (7.2, 7.4, 7.5, 7.6)
a. molecular formula
c. molar mass
b. empirical formula
d. mass percent composition
(a)

Interpretation: To find the empirical formula of dipyrithione.
Concept Introduction: Empirical formula is the simplest ratio of different elements in a compound.
Answer to Problem 61UTC
The empirical formula of dipyrithione is C5H4NOS
Explanation of Solution
The molecular formula of dipyrithione is C10H8N2O2S2 The subscript of each element is divided by 2. 2 is the minimum number of atoms of elements N, O and S.
Thus the empirical formula is C5H4NOS
(b)

Interpretation: To find the molar mass of dipyrithione.
Concept Introduction: Molar mass is found by adding the atomic mass of each element that makes up the compound.
Answer to Problem 61UTC
Molar mass of dipyrithione = 252 g/mol
Explanation of Solution
The molecular formula of dipyrithione is C10H8N2O2S2 Atomic mass of C = 12 g/mol
Atomic mass of H = 1 g/mol
Atomic mass of N = 14 g/mol
Atomic mass of O = 16 g/mol
Atomic mass of S = 32 g/mol
Molar mass of dipyrithione, C10H8N2O2S2 =
(c)

Interpretation: To find the mass percent of O in dipyrithione.
Concept Introduction:
Answer to Problem 61UTC
Mass percent of O in dipyrithione = 12.7 %
Explanation of Solution
The molecular formula of dipyrithione is C10H8N2O2S2 Since from the molecular formula of dipyrithione it’s clear that dipyrithione contains 2 atoms of oxygen so, Mass percent of O in dipyrithione =
(d)

Interpretation: To find the grams of C in 2.50 g of dipyrithione.
Concept Introduction: An arithmetical multiplier which is used for converting a quantity expressed in one unit into another equivalent set of units is said to be conversion factor.
Answer to Problem 61UTC
11.9 g of C is present in 2.50 g of dipyrithione.
Explanation of Solution
The molecular formula of dipyrithione is C10H8N2O2S2 Since from the molecular formula of dipyrithione it’s clear that dipyrithione contains 10 atoms of carbon so,
Thus,
Hence, the mass of carbon in 25.0 g of dipyrithione is 11.9 g.
(e)

Interpretation: To find the moles of dipyrithione in 25.0 g of dipyrithione.
Concept Introduction:
The relationship between mass, moles, and molar mass:
Answer to Problem 61UTC
Moles of dipyrithione = 0.0992 mol
Explanation of Solution
The relationship between mass, moles, and molar mass:
Mass of dipyrithione is 25.0 g (given)
Molar mass of dipyrithione is 252 g/mol.
Moles of dipyrithione =
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Chapter 7 Solutions
Basic Chemistry
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