# A liquid has a molecular weight of 105.141g/mol. Its density is 1.173g/mL. What is the molarity of the pure liquid?

##### 1 Answer

#### Explanation:

Your strategy here will be to pick a sample of this compound and try to find how many **moles** it contains **per liter**.

Although molarity is usually defined as *moles of solute* per **liters** of solution, you can extend this concept to *pure liquids*, provided that you figure out how many moles you'd get **per liter** of pure liquid.

As you know, a substance's *molar mass* tells you the mass of **one mole** of that substance. In this case, the liquid is said to have a molar mass of **one mole** will have a mass of

To make the calculations easier, let's pick a *one mole*. You know from the given density that **every milliliter** of this liquid will have a mass of

This means that our sample will occupy a volume of

#105.141 color(red)(cancel(color(black)("g"))) * "1 mL"/(1.173color(red)(cancel(color(black)("g")))) = "89.63427 mL"#

Convert this volume **to liters**

#89.63427 color(red)(cancel(color(black)("mL"))) * "1 L"/(1000color(red)(cancel(color(black)("mL")))) = "0.08963427 L"#

Finally, the molarity of the solution will be - remember that our sample contains exactly **one mole** of this liquid

#color(blue)(c = n/V)#

#c = "1 mole"/"0.08963427 L" = color(green)("11.16 M")#

The answer is rounded to four sig figs, the number of sig figs you have for the density of the liquid.