Question

What would be the resulting molarity of a solution made by dissolving 31.3 grams of Ca(OH)2 in enough water to make a 1050-milliliter solution?

Answer 1

\[Molarity = \frac{Moles}{Litres}\]

1L = 1000mL

\[Moles = \frac{Grams}{Molecular Mass}\]

Note Molecular mass has units g/mol

Answer 2

You can find the molecular mass of a compound by looking at your periodic table and adding the weights up for each element in the compound

for example the molar mass of HCl is

Molar Mass of H + Molar Mass of Cl
1.00794g/mol + 35.453g/mol = Molar Mass of Cl

Answer 3

Molar Mass = Molecular Mass

Any questions ask or if you get stuck show me your work and I can help you

Answer 4

I pretty much just gave you the answer though, these questions are plug and chug questions you should memorize both those formulas btw

Answer 5

Ok

Answer 6

Just to avoid confusion

if you want to find the molecular mass of
H2O for example

it would be

Molar mass of H + Molar Mass of H + Molar Mass of O = Molar Mass of H2O

Answer 7

So it would be 40.078/mol + (15.999*1.008)2/mol... like this

Answer 8

(15.999*1.008)+(15.999*1.008)

Answer 9

the units are g/mol not 1/mol

secondly you need to add the molecular mass of each atom
so in your case
Ca(OH)2
broken down
Ca + OH + OH
you have the atoms
Ca + H + O + O + H
add their molecular mass

Answer 10

to get the molecular mass of the compound

Answer 11

its like if you had 12 apples all had different weights it doesn't make any sense to multiply their weights, you just need to add them all up.

Answer 12

Molar mass is essentially the weight of an atom per 1 mole of it.

so 1 mole of calcium = 40.078grams

Answer 13

we want the weight of the entire compound per 1 mole, to do that we have to add them all up

Answer 14

a mole being avagadros number of atoms or molecules

Answer 15

ok so 40.078 + 1.008 + 15.998 +1.008 +15.998

Answer 16

Which is 79.04

Answer 17

i meant 74.09

Answer 18

looks good to me, make sure to use the units g/mol

Answer 19

showing units is important

Answer 20

Then do we divide this

Answer 21

ok do we put something over this or am I just over thinking it

Answer 22

nvm no you are right lol

Answer 23

keep going convert to moles then, convert mL to Liters and plug into molarity formula

Answer 24

\[Moles = \frac{Grams of Ca(OH)_2}{79.04g/mol}\]

Answer 25

74.09/100=0.7409