How would you the mass in grams of #4.52 xx10^-3# #"C"_20"H"_42"#? Use the molar masses: C = 12.0 g/mole; H = 1.0 g/mol.

2 Answers
anor277
Dec 23, 2017

Take the product...#"molar quantity"xx"molar mass"#; I gets a tad over #1*g#...

Explanation:

You got the molar quantity...#4.52xx10^-3*mol#...(you have not specified the units in your question, but I assume that these units pertain); and multiply these units by the molar mass...

#4.52xx10^-3*molxx(20xx12_("atomic mass of carbon")+42xx1_("atomic mass of hydrogen"))*g*mol^-1=??*g#

Meave60
Dec 23, 2017

The mass of #4.52xx"10"^(-3) "mol C"_20"H"_42"# is #"1.27 g"#.

Explanation:

If the mass of #4.52xx"10"^(-3) "mol C"_20"H"_42"# is what you are looking for:

Determine the molar mass of #"C"_20"H"_42"#.

#"Molar mass"##color(white)(.)## "C"_20"H"_42: ##(20xx"12.0 g/mol C")+(42xx"1.0 g/mol H")="282 g/mol C"_20"H"_42"#

Mass of #4.52xx"10"^(-3) "mol C"_20"H"_42"#

Multiply mol #"C"_20"H"_42"# by its molar mass.

#4.52xx"10"^(-3) color(red)cancel(color(black)("mol C"_20"H"_42))xx(282"g C"_20"H"_42)/(1color(red)cancel(color(black)("mol C"_20"H"_42)))="1.27 g C"_20"H"_42"# rounded to three significant figures

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