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Chapter 4: Problem 33

What are the molarities of the following solutes? (a) sucrose \(\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)\) if \(150.0 \mathrm{g}\) is dissolved per \(250.0 \mathrm{mL}\) of water solution (b) urea, \(\mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2},\) if \(98.3 \mathrm{mg}\) of the \(97.9 \%\) pure solid is dissolved in \(5.00 \mathrm{mL}\) of aqueous solution (c) methanol, \(\mathrm{CH}_{3} \mathrm{OH},(d=0.792 \mathrm{g} / \mathrm{mL})\) if \(125.0 \mathrm{mL}\) is dissolved in enough water to make 15.0 L of solution

Short Answer

Expert verified
The molarities for the solutes are; (a) Sucrose solution: 2.08 M. (b) Urea solution: 3.13 M. (c) Methanol solution: 0.206 M.

Step by step solution

01

Compute Molarity of Sucrose Solution

Molar mass of sucrose \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) is \(342.3 \mathrm{g/mol}\). First, convert the given mass of sucrose (150.0 g) to moles using the molar mass. Secondly, the volume of water (250.0 mL) should be converted to liters, since molarity is defined in terms of liters of solution. Lastly, use the formula for molarity which is \(\text{M} = \frac{\text{moles of solute}}{\text{liters of solution}}\).
02

Compute Molarity of Urea Solution

The molar mass of urea, \(\mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2}\), is \(60.06 \mathrm{g/mol}\). Given mass (98.3 mg) needs to be first converted to grams. Then, to take into account the purity, multiply the mass by 0.979. Convert this mass to moles using the molar mass. Convert the volume of water (5.00 mL) to liters. Finally, determine the molarity by dividing moles of solute by liters of solution.
03

Compute Molarity of Methanol Solution

The molar mass of methanol, \(\mathrm{CH}_{3} \mathrm{OH}\), is \(32.04 \mathrm{g/mol}\). With given volume (125.0 mL) and the density (0.792 g/mL), calculate the mass of methanol in grams. Convert this mass to moles. Then, use the total solution volume (15.0 L) to determine the molarity.

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Most popular questions from this chapter

Iron ore is impure \(\mathrm{Fe}_{2} \mathrm{O}_{3} .\) When \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) is heated with an excess of carbon (coke), metallic iron and carbon monoxide gas are produced. From a sample of ore weighing \(938 \mathrm{kg}, 523 \mathrm{kg}\) of pure iron is obtained. What is the mass percent \(\mathrm{Fe}_{2} \mathrm{O}_{3},\) by mass, in the ore sample, assuming that none of the impurities contain Fe?

Given a \(0.250 \mathrm{M} \mathrm{K}_{2} \mathrm{CrO}_{4}\) stock solution, describe how you would prepare a solution that is \(0.0125 \mathrm{M}\) \(\mathrm{K}_{2} \mathrm{CrO}_{4} .\) That is, what combination(s) of pipet and volumetric flask would you use? Typical sizes of volumetric flasks found in a general chemistry laboratory are \(100.0,250.0,500.0,\) and \(1000.0 \mathrm{mL},\) and typical sizes of volumetric pipets are 1.00,5.00,10.00 \(25.00,\) and \(50.00 \mathrm{mL}\)

What volume of \(0.0175 \mathrm{M} \mathrm{CH}_{3} \mathrm{OH}\) must be added to \(50.0 \mathrm{mL}\) of \(0.0248 \mathrm{M} \mathrm{CH}_{3} \mathrm{OH}\) so that the resulting solution has a molarity of exactly \(0.0200 \mathrm{M}\) ? Assume that the volumes are additive.

What volume of \(0.149 \mathrm{M} \mathrm{HCl}\) must be added to \(1.00 \times 10^{2} \mathrm{mL}\) of \(0.285 \mathrm{M} \mathrm{HCl}\) so that the resulting solution has a molarity of \(0.205 \mathrm{M} ?\) Assume that the volumes are additive.

Nitric acid, \(\mathrm{HNO}_{3}\), can be manufactured from ammonia, \(\mathrm{NH}_{3}\), by using the three reactions shown below. $$\begin{aligned} &\text { Step 1: 4 NH }_{3}(\mathrm{g})+5 \mathrm{O}_{2}(\mathrm{g}) \rightarrow 4 \mathrm{NO}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})\\\ &\text { Step 2: } 2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{NO}_{2}(\mathrm{g})\\\ &\text { Step 3: } 3 \mathrm{NO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{HNO}_{3}(\mathrm{aq})+\mathrm{NO}(\mathrm{g}) \end{aligned}$$ What is the maximum number of moles of \(\mathrm{HNO}_{3}\) that can be obtained from 4.00 moles of \(\mathrm{NH}_{3}\) ? (Assume that the NO produced in step 3 is not What is the maximum number of moles of \(\mathrm{HNO}_{3}\) that can be obtained from 4.00 moles of \(\mathrm{NH}_{3}\) ? (Assume that the NO produced in step 3 is not recycled back into step 2.) (a) 1.33 mol; (b) 2.00 mol; (c) 2.67 mol; (d) 4.00 mol; (e) 6.00 mol.
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