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Ch.3 - Mass Relationships in Chemical Reactions
Chapter 3, Problem 5

How many moles of chloride ions are in 7.75 g of FeCl3? (LO 3.4) (a) 4.78 * 10^-2 (b) 1.59 * 10^-2 (c) 1.43 * 10^-1 (d) 1.91 * 10^-1

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To find the number of moles in a given mass of a compound, you first need to calculate its molar mass by summing the atomic masses of all the atoms in its formula. For FeCl3, the molar mass is calculated by adding the atomic mass of iron (Fe) and three times the atomic mass of chlorine (Cl).
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Stoichiometry

Stoichiometry is the area of chemistry that deals with the relationships between the quantities of reactants and products in chemical reactions. In this context, it helps determine how many moles of chloride ions are produced from a given amount of FeCl3. Since each formula unit of FeCl3 contains three chloride ions, stoichiometry allows us to convert moles of FeCl3 to moles of Cl- ions.
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Conversion of Grams to Moles

To convert grams of a substance to moles, you use the formula: moles = mass (g) / molar mass (g/mol). This conversion is essential for solving the problem, as it allows you to determine how many moles of FeCl3 are present in 7.75 g, which can then be used to find the corresponding moles of chloride ions based on the stoichiometric ratio.
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Related Practice
Textbook Question
What are the coefficients in the balanced equation for the combustion of ethanol? (LO 3.2) (a) 1, 3, 2, 3 (b) 2, 3, 4, 3 (c) 2, 7, 4, 6 (d) 1, 4, 2, 3
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Textbook Question

The ball-and-stick molecular model is a representation of caf-feine. Calculate the molecular weight of caffeine. (Gray = C, red = O, blue = N, ivory = H.) (LO 3.3)

(a) 194.2 (b) 182.2 (c) 192.2 (d) 180.2

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Textbook Question

A can of diet soda contains 180 mg of the low-calorie sugar substitute aspartame (C14H18N2O5). How many molecules of aspartame are in the can of soda? (LO 3.4) (a) 3.7 * 10^23 (b) 3.7 * 10^20 (c) 3.2 * 10^25 (d) 1.2 * 10^22

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Textbook Question
One way to make coal burning better for the environment is to remove carbon dioxide from the exhaust gases released from power plants using a compound containing an amine (-NH2) group. The reaction between carbon dioxide and monoethanolamine is: CO2(g) + 2 HOCH2CH2NH2(aq) -> HOCH2CH2NH3 +(aq) + HOCH2CH2NHCO2-(aq) What mass of monoethanoloamine is required to react with 1.0 kg of carbon dioxide? (LO 3.5) (a) 2.8 kg (b) 1.1 kg (c) 0.93 kg (d) 0.53 kg
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Textbook Question
If 42.85 grams of salicylic acid reacts with excess acetic anhydride and produces 48.47 grams of aspirin, what is the percent yield of the reaction? (LO 3.6) (a) 88.40% (b) 64.69% (c) 86.72% (d) 78.74%
851
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Textbook Question
The diagram represents a mixture of AB2 and B2 before it reacts to form AB3. (Red spheres = A, blue spheres = B.) Which reactant is limiting, and how many AB3 molecules are formed? (LO 3.7)

(a) B2 is limiting, and 10 molecules of AB3 are formed. (b) B2 is limiting, and 4 molecules of AB3 are formed. (c) AB2 is limiting, and 6 molecules of AB3 are formed. (d) AB2 is limiting, and 4 molecules of AB3 are formed
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