Question #1caee

2 Answers
Dec 11, 2017

Answer:

#"CO"_2#

Explanation:

The question essentially wants you to figure out the molar mass, i.e. the mass of exactly #1# mole, of this compound.

Now, the important thing to keep in mind here is that #1# mole of a molecular substance contains #6.022 * 10^(23)# molecules of that substance #-># this is known as Avogadro's constant.

In other words, in order to have #1# mole of a molecular substance, you need to have a sample that contains #.6022 * 10^(23)# molecules of that substance.

This means that the molar mass of the compound will give you the mass of #6.022 * 10^(23)# molecules.

Since you already know that #4.67 * 10^(16)# molecules have a mass of #3.41 * 10^(-6)# #"g"#, you can use this as a conversion factor to find the mass of #6.022 * 10^(23)# molecules.

#6.022 * 10^(23) color(red)(cancel(color(black)("molecules"))) * (3.41 * 10^(-6)color(white)(.)"g")/(4.67 * 10^(16)color(red)(cancel(color(black)("molecules"))))= "44.0 g"#

You can thus say that you have #"44.0 g"# for every #6.022 * 10^(23)# molecules, i.e. #1# mole of this compound, which means that you have

#"molar mass" = "44.0 g mol"^(-1) -># three sig figs

Based on the options given to you, the closest match is carbon dioxide, #"CO"_2#, which has a molar mass of #"44.01 g mol"^(-1)#

Dec 11, 2017

Answer:

a) #CO_2#

Explanation:

The mole is related to the mass by the molecular weight. We can calculate the ratio of molecules to those of a mole and compare that to the ratio of compound molecular weights to the sample mass. The one with the equal ratios is the answer.

Ratio of molecules to a Mole: #(4.67 xx 10^16)/(6.022 xx 10^23)#
#= 7.75 xx 10^(-8)#

#(Mass)/("Molecular Weight") = (3.41 xx 10^(-6))/("M.W.")#

#CO_2 = (3.41 xx 10^(-6))/44 = 7.75 xx 10^(-8)#
#CH_4 = (3.41 xx 10^(-6))/16 = 2.13 xx 10^(-8)#
#NH_3 = (3.41 xx 10^(-6))/17 = 2.01 xx 10^(-8)#
#H_2O = (3.41 xx 10^(-6))/18 = 1.89 xx 10^(-8)#