The molecular weight of CaCl2 is 110.98 g/mol. In order to make up 500.0 mL of a 0.500 M solution, you need 27.7 g.

How is this true?

Question

The molecular weight of CaCl2 is 110.98 g/mol. In order to make up 500.0 mL of a 0.500 M solution, you need 27.7 g.

How is this true?

desmarie · Answer

@Photon336

desmarie · Answer

@radar

photon336 · Answer

$$Molarity = \frac{ moles }{ L }$$

photon336 · Answer

What we need to do is this we know what the molarity is and we know our volume right?

desmarie · Answer

well actually 27.7 is the answer but I dont know how they got that answer.

photon336 · Answer

so we can easily check this by doing the following this is what we're going to do.

$$molarity*volume*molar~mass = \frac{ moles }{ L }*L*\frac{ grams }{ mol }$$

photon336 · Answer

$$0.5\frac{ moles }{ Liters }*0.5~Liters*110.98\frac{ grams }{ mole } = grams~CaCl_{2}$$

desmarie · Answer

ok I get how they go the 27.7 now thanks that helped a lot.

photon336 · Answer

We've got to get to our answer too, take a look at what I did. essentially molarity is the number of moles per liter of solution. we want to find the number of grams of our compound in that solution. all we need to do is multiply the molarity by the volume in Liter to give us the moles of the compound. then the next step is easy.

desmarie · Answer

ok thanks I really appreciate it I wish I could give you more than 1 medal.

photon336 · Answer

you can even try this out yourself. practice 

How many grams of NaCL are in a  0.25M solution when you know you have .2 Liters of of NaCl?

desmarie · Answer

would the answer be 2.3 g?

photon336 · Answer

Show me your work

desmarie · Answer

0.2 moles/liters times 0.2 liters times 58.44 grams/mole = grams of NaCl