The density of a 20.0% by mass ethylene glycol (C2H6O2) solution in water is 1.03 g/mL. Find the molarity of the solution.
Ch.5 - Introduction to Solutions and Aqueous Solutions
Chapter 5, Problem 65c,d
Determine whether each reaction is a redox reaction. For each redox reaction, identify the oxidizing agent and the reducing agent. c. Pb(NO3)2(aq) + Na2SO4(aq) → PbSO4(s) + 2 NaNO3(aq) d. HBr(aq) + KOH(aq) → H2O(l) + KBr(aq)
Verified step by step guidance1
Step 1: Understand the concept of a redox reaction. A redox reaction involves the transfer of electrons between two species. It consists of two half-reactions: oxidation (loss of electrons) and reduction (gain of electrons).
Step 2: Assign oxidation states to each element in the reactants and products for reaction c: Pb(NO_3)_2(aq) + Na_2SO_4(aq) \(\rightarrow\) PbSO_4(s) + 2 NaNO_3(aq).
Step 3: Compare the oxidation states of each element before and after the reaction in c. If there is a change in oxidation states, it is a redox reaction. If not, it is not a redox reaction.
Step 4: Repeat steps 2 and 3 for reaction d: HBr(aq) + KOH(aq) \(\rightarrow\) H_2O(l) + KBr(aq).
Step 5: For any reaction identified as a redox reaction, determine the oxidizing agent (species that is reduced) and the reducing agent (species that is oxidized).

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Redox Reactions
Redox reactions, or reduction-oxidation reactions, involve the transfer of electrons between two species. In these reactions, one substance is oxidized (loses electrons) while another is reduced (gains electrons). Identifying redox reactions requires analyzing changes in oxidation states of the elements involved.
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Oxidizing and Reducing Agents
The oxidizing agent is the substance that gains electrons and is reduced in a redox reaction, while the reducing agent is the substance that loses electrons and is oxidized. Understanding these roles is crucial for identifying which species undergo changes in oxidation state during the reaction.
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Precipitation Reactions
Precipitation reactions occur when two aqueous solutions react to form an insoluble solid, known as a precipitate. In the given reactions, it is important to recognize that not all reactions are redox; some may simply involve the formation of a precipitate without electron transfer.
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Related Practice
Textbook Question
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What is the oxidation state of Cl in each ion? a. ClO- b. ClO2- c. ClO3- d. ClO4-
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Determine whether each reaction is a redox reaction. For each redox reaction, identify the oxidizing agent and the reducing agent. a. 4 Li(s) + O2(g) → 2 Li2O(s) b. Mg(s) + Fe2+(aq) → Mg2+(aq) + Fe(s)
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Find the percent by mass of sodium chloride in a 1.35 M NaCl solution. The density of the solution is 1.05 g/mL.
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What is the oxidation state of Cr in each compound? c. Cr2O3
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Determine whether each reaction is a redox reaction. For each redox reaction, identify the oxidizing agent and the reducing agent. a. Al(s) + 3 Ag+(aq) → Al3+(aq) + 3 Ag(s) b. SO3(g) + H2O(l) → H2SO4(aq) c. Ba(s) + Cl2(g) → BaCl2(s) d. Mg(s) + Br2(l) → MgBr2(s)
