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Chapter 4: Problem 113

An organic liquid is either methyl alcohol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\) ethyl alcohol \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right),\) or a mixture of the two. A 0.220-g sample of the liquid is burned in an excess of \(\mathrm{O}_{2}(\mathrm{g})\) and yields \(0.352 \mathrm{g} \mathrm{CO}_{2}(\mathrm{g}) .\) Is the liquid a pure alcohol or a mixture of the two?

Short Answer

Expert verified
The liquid is a mixture of methyl alcohol and ethyl alcohol.

Step by step solution

01

Write down the balanced chemical equations for the combustion of methyl alcohol and ethyl alcohol

Balanced chemical equation for the combustion of methyl alcohol: \(2 CH_3OH + 3 O_2 \rightarrow 2 CO_2 + 4 H_2O\) Balanced chemical equation for the combustion of ethyl alcohol: \(C_2H_5OH + 3 O_2 \rightarrow 2 CO_2 + 3 H_2O\)
02

Calculate the molar mass of CO2, methyl alcohol and ethyl alcohol

The molar mass of CO2 = 12.01 g/mol (for C) + 2*16.00 g/mol (for 2 O) = 44.01 g/mol The molar mass of methyl alcohol (CH3OH) = 12.01 g/mol (for C) + 3*1.01 g/mol (for 3 H) + 16.00 g/mol (for O)+ 1.01 g/mol (for H) = 32.04 g/mol The molar mass of ethyl alcohol (C2H5OH) =2*12.01 g/mol (for 2 C) + 5*1.01 g/mol (for 5 H) + 16.00 g/mol (for O) + 1.01 g/mol (for H) = 46.07 g/mol
03

Determine the moles of CO2 and the alcohol on combustion

The moles of CO2 formed = mass of CO2/molar mass = 0.352 g/44.01 g/mol = 0.008 mol The moles of methyl alcohol based on the balanced equation for its combustion = moles of CO2 / 2 = 0.008 mol / 2 = 0.004 mol The moles of ethyl alcohol based on the balanced equation for its combustion = moles of CO2 / 2 = 0.008 mol / 2 = 0.004 mol
04

Compare the calculated moles of the alcohol with the moles of the alcohol in the sample

To get the moles of the alcohol in the sample, we divide the sample mass by the molar mass: If the sample was methyl alcohol, the moles would be sample mass/molar mass= 0.220 g/32.04 g/mol = 0.007mol. If the sample was ethyl alcohol, the moles would be sample mass/molar mass = 0.220 g/46.07 g/mol = 0.005 mol. Comparing these values to the moles of alcohol on combustion, it can be seen that neither match. Thus, the liquid is a mixture of the two alcohols.

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Most popular questions from this chapter

A sulfide of iron, containing \(36.5 \%\) S by mass, is heated in \(\mathrm{O}_{2}(\mathrm{g}),\) and the products are sulfur dioxide and an oxide of iron containing \(27.6 \%\) O, by mass. Write a balanced chemical equation for this reaction.

Titanium tetrachloride, \(\mathrm{TiCl}_{4}\) is prepared by the reaction below. $$\begin{aligned} &3 \mathrm{TiO}_{2}(\mathrm{s})+4 \mathrm{C}(\mathrm{s})+6 \mathrm{Cl}_{2}(\mathrm{g}) \longrightarrow 3 \mathrm{TiCl}_{4}(\mathrm{g})+2 \mathrm{CO}_{2}(\mathrm{g})+2 \mathrm{CO}(\mathrm{g}) \end{aligned}$$ What is the maximum mass of \(\mathrm{TiCl}_{4}\) that can be obtained from \(35 \mathrm{g} \mathrm{TiO}_{2^{\prime}} 45 \mathrm{g} \mathrm{Cl}_{2^{\prime}}\) and \(11 \mathrm{g} \mathrm{C} ?\)

Nitrogen gas, \(\mathrm{N}_{2}\), can be prepared by passing gaseous ammonia over solid copper(II) oxide, \(\mathrm{CuO}\), at high temperatures. The other products of the reaction are solid copper, \(\mathrm{Cu},\) and water vapor. In a certain experiment, a reaction mixture containing \(18.1 \mathrm{g} \mathrm{NH}_{3}\) and \(90.4 \mathrm{g}\) CuO yields \(6.63 \mathrm{g} \mathrm{N}_{2}\). Calculate the percent yield for this experiment.

A small piece of zinc is dissolved in \(50.00 \mathrm{mL}\) of \(1.035 \mathrm{M}\) HCl. At the conclusion of the reaction, the concentration of the \(50.00 \mathrm{mL}\) sample is redetermined and found to be \(0.812 \mathrm{M} \mathrm{HCl} .\) What must have been the mass of the piece of zinc that dissolved? $$\mathrm{Zn}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{ZnCl}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})$$

Consider the reaction below: \(2 \mathrm{AgNO}_{3}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{S}(\mathrm{aq}) \longrightarrow\) $$ \mathrm{Ag}_{2} \mathrm{S}(\mathrm{s})+2 \mathrm{NaNO}_{3}(\mathrm{aq}) $$ (a) How many grams of \(\mathrm{Na}_{2} \mathrm{S}(\mathrm{s})\) are required to react completely with \(27.8 \mathrm{mL}\) of \(0.163 \mathrm{M} \mathrm{AgNO}_{3} ?\) (b) How many grams of \(\mathrm{Ag}_{2} \mathrm{S}(\mathrm{s})\) are obtained from the reaction in part (a)?
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