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Ch.4 - Reactions in Aqueous Solution
McMurry - Chemistry 8th Edition
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모든 교과서McMurry 8th EditionCh.4 - Reactions in Aqueous Solution문제 154a
4장, 문제 154a

To 100.0 mL of a solution that contains 0.120 M Cr(NO3)2 and 0.500 M HNO3 is added to 20.0 mL of 0.250 M K2Cr2O7. The dichromate and chromium(II) ions react to give chromium(III) ions. (a) Write a balanced net ionic equation for the reaction.

검증된 단계별 안내
1
Identify the reactants and products in the reaction: Cr(NO_3)_2 provides Cr^{2+} ions, K_2Cr_2O_7 provides Cr_2O_7^{2-} ions, and the reaction produces Cr^{3+} ions.
Write the unbalanced net ionic equation: Cr_2O_7^{2-} + Cr^{2+} \(\rightarrow\) Cr^{3+}.
Balance the chromium atoms: There are 2 chromium atoms in Cr_2O_7^{2-}, so you need 2 Cr^{3+} ions on the product side.
Balance the charges: The total charge on the reactant side is 2- from Cr_2O_7^{2-} and 2+ from Cr^{2+}, which sums to 0. The product side has 2 Cr^{3+} ions, which is 6+. To balance, add 6 electrons to the product side.
The balanced net ionic equation is: Cr_2O_7^{2-} + 6 Cr^{2+} + 14 H^+ \(\rightarrow\) 7 Cr^{3+} + 7 H_2O.

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
영상 길이:
7m

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Net Ionic Equations

A net ionic equation represents the chemical species that are involved in a reaction, excluding spectator ions that do not participate. It focuses on the actual chemical change occurring in the solution, providing a clearer picture of the reaction. To write a net ionic equation, one must first write the complete ionic equation and then remove the ions that appear unchanged on both sides.
추천 영상:
가이드 코스
00:51
Net Ionic Equations

Oxidation States

Oxidation states (or oxidation numbers) indicate the degree of oxidation of an atom in a compound. They help in identifying which species are oxidized and reduced during a chemical reaction. In the context of the given reaction, understanding the oxidation states of chromium in Cr(NO3)2, K2Cr2O7, and the resulting chromium(III) ions is essential for balancing the equation correctly.
추천 영상:
가이드 코스
02:42
Oxidation Numbers

Stoichiometry of Reactions

Stoichiometry involves the calculation of reactants and products in chemical reactions based on the balanced equation. It allows chemists to predict the amounts of substances consumed and produced. In this question, stoichiometry is crucial for determining the molar ratios of chromium(II) ions and dichromate ions that react to form chromium(III) ions, which is necessary for writing the balanced net ionic equation.
추천 영상:
가이드 코스
01:16
Stoichiometry Concept
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교과서 질문

Sodium nitrite, NaNO2, is frequently added to processed meats as a preservative. The amount of nitrite ion in a sample can be determined by acidifying to form nitrous acid (HNO2), letting the nitrous acid react with an excess of iodide ion, and then titrating the I3 - ion that results with thiosulfate solution in the presence of a starch indicator. The unbalanced equations are (1) (2) (a) Balance the two redox equations.

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교과서 질문
Four solutions are prepared and mixed in the following order: (a) Start with 100.0 mL of 0.100 M BaCl2 (b) Add 50.0 mL of 0.100 M AgNO3 (c) Add 50.0 mL of 0.100 M H2SO4 (d) Add 250.0 mL of 0.100 M NH3. Write an equation for any reaction that occurs after each step, and calculate the concentrations of Ba2+, Cl-, NO3-, NH3, and NH4+ in the final solution, assuming that all reactions go to completion.
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교과서 질문

Element M is prepared industrially by a two-step procedure according to the following (unbalanced) equations:

Assume that 0.855 g of M2O3 is submitted to the reaction sequence. When the HCl produced in step (2) is dissolved in water and titrated with 0.511 M NaOH, 144.2 mL of the NaOH solution is required to neutralize the HCl. (a) Balance both equations.

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교과서 질문
Assume that you dissolve 10.0 g of a mixture of NaOH and Ba(OH)2 in 250.0 mL of water and titrate with 1.50 M hydrochloric acid. The titration is complete after 108.9 mL of the acid has been added. What is the mass in grams of each substance in the mixture?
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교과서 질문

Sodium nitrite, NaNO2, is frequently added to processed meats as a preservative. The amount of nitrite ion in a sample can be determined by acidifying to form nitrous acid (HNO2), letting the nitrous acid react with an excess of iodide ion, and then titrating the I3 - ion that results with thiosulfate solution in the presence of a starch indicator. The unbalanced equations are (1) (2) (b) When a nitrite-containing sample with a mass of 2.935 g was analyzed, 18.77 mL of 0.1500 M Na2S2O3 solution was needed for the reaction. What is the mass percent of NO2- ion in the sample?

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교과서 질문

(b) Calculate the concentrations of all ions in the solution after reaction. Check your concentrations to make sure that the solution is electrically neutral.

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