Question

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.

Answer 1

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`

Answer 2

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