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Chapter 6: Problem 29

Calculate the molarity of each of these solutions. a. A 5.623 -g sample of NaHCO, is dissolved in enough water to make \(250.0 \mathrm{mL}\) of solution. b. A \(184.6-\mathrm{mg}\) sample of \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) is dissolved in enough water to make \(500.0 \mathrm{mL}\) of solution. c. A \(0.1025-\mathrm{g}\) sample of copper metal is dissolved in \(35 \mathrm{mL}\) of concentrated HNO_to form \(\mathrm{Cu}^{2+}\) ions and then water is added to make a total volume of \(200.0 \mathrm{mL}\). (Calculate the molarity of \(\mathrm{Cu}^{2+}\).)

Short Answer

Expert verified
The molarities of the given solutions are as follows: a. The molarity of NaHCO3 solution is \(0.268 M\) b. The molarity of K2Cr2O7 solution is \(0.00126 M\) c. The molarity of Cu2+ ions in the solution is \(0.00808 M\)

Step by step solution

01

a. Calculate moles of NaHCO3

To convert the mass of NaHCO3 to moles, we first need to find the molar mass of NaHCO3. The molar mass of NaHCO3 is: 23 (Na) + 1 (H) + 12 (C) + 16x3 (O) = 84 g/mol Now we can convert 5.623 g of NaHCO3 to moles: 5.623 g / 84 g/mol = 0.067 moles of NaHCO3
02

a. Convert volume to liters

The volume of the solution is given in milliliters (mL). We need to convert it to liters (L): 250.0 mL × (1 L / 1000 mL) = 0.250 L
03

a. Calculate molarity

Now we can calculate the molarity using the formula M = moles of solute/liters of solution: M = 0.067 moles NaHCO3 / 0.250 L = 0.268 M
04

b. Calculate moles of K2Cr2O7

To convert the mass of K2Cr2O7 to moles, we first need to find the molar mass of K2Cr2O7. The molar mass of K2Cr2O7 is: (2x39) (K) + (2x52) (Cr) + (7x16) (O) = 294 g/mol Now we can convert 184.6 mg of K2Cr2O7 to moles: 184.6 mg × (1 g / 1000 mg)= 0.1846 g 0.1846 g / 294 g/mol = 0.000628 moles of K2Cr2O7
05

b. Convert volume to liters

The volume of the solution is given in milliliters (mL). We need to convert it to liters (L): 500.0 mL × (1 L / 1000 mL) = 0.500 L
06

b. Calculate molarity

Now we can calculate the molarity using the formula M = moles of solute/liters of solution: M = 0.000628 moles K2Cr2O7 / 0.500 L = 0.00126 M
07

c. Calculate moles of Cu

To convert the mass of Cu to moles, we first need to find the molar mass of Cu. The molar mass of Cu is: 63.5 g/mol Now we can convert 0.1025 g of Cu to moles: 0.1025 g / 63.5 g/mol = 0.001615 moles of Cu
08

c. Convert volume to liters

The volume of the solution after adding water is given in milliliters (mL). We need to convert it to liters (L): 200.0 mL × (1 L / 1000 mL) = 0.200 L
09

c. Calculate molarity

Now we can calculate the molarity of Cu2+ ions using the formula M = moles of solute/liters of solution: M = 0.001615 moles Cu / 0.200 L = 0.00808 M In summary: a. The molarity of NaHCO3 solution is 0.268 M b. The molarity of K2Cr2O7 solution is 0.00126 M c. The molarity of Cu2+ ions in the solution is 0.00808 M

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Most popular questions from this chapter

Zinc and magnesium metal each react with hydrochloric acid according to the following equations: $$ \begin{array}{c} \mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g) \\ \mathrm{Mg}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{MgCl}_{2}(a q)+\mathrm{H}_{2}(g) \end{array} $$ A \(10.00-\mathrm{g}\) mixture of zinc and magnesium is reacted with the stoichiometric amount of hydrochloric acid. The reaction mixture is then reacted with \(156 \mathrm{mL}\) of \(3.00 \mathrm{M}\) silver nitrate to produce the maximum possible amount of silver chloride. a. Determine the percent magnesium by mass in the original mixture. b. If \(78.0 \mathrm{mL}\) of HCl was added, what was the concentration of the HCl?

In the spectroscopic analysis of many substances, a series of standard solutions of known concentration are measured to generate a calibration curve. How would you prepare standard solutions containing \(10.0,25.0,50.0,75.0,\) and \(100 .\) ppm of copper from a commercially produced 1000.0 -ppm solution? Assume each solution has a final volume of \(100.0 \mathrm{mL}\). (See Exercise 123 for definitions.)

Using the general solubility rules given in Table \(6-1,\) name three reagents that would form precipitates with each of the following ions in aqueous solution. Write the net ionic equation for each of your suggestions. a. chloride ion d. sulfate ion b. calcium ion e. mercury(I) ion, \(\mathrm{Hg}_{2}^{2+}\) c. iron(III) ion f. silver ion

For the following chemical reactions, determine the precipitate produced when the two reactants listed below are mixed together. Indicate "none" if no precipitate will form.

Write net ionic equations for the reaction, if any, that occurs when aqueous solutions of the following are mixed. a. chromium(III) chloride and sodium hydroxide b. silver nitrate and ammonium carbonate c. copper(II) sulfate and mercury(I) nitrate d. strontium nitrate and potassium iodide
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