Taking Molar Mass and finding # of moles/mass/particles in the equation?

Question

problems such as---
1. 689.3 grams of aluminum sulfate (moles)
2. 4.69 X 10^25 atoms of gold (moles)
3. 1.50 moles of calcium chloride (grams)
4. 1.26 X 10^24 formula units of sodium phosphate (grams)
5. 2.57 moles of potassium nitrate (particles)
6. 42.8 grams of magnesium sulfate (particles)

i'm fine on finding the molecular mass, i don't understand how to use dimensional (sp?) analysis to take that and find out what the answer needs to be in parenthesis.

Answer 1

Use these conversion factors

moles = g/MM (g x Imol/MM)
g = MM x moles
moles = numbers of particles/ (6.022E23) = [#particles x 1mole/6.022e23]
particles = moles x (6.022E23)/1mol

Answer 2

Molar mass is the sum of each and every of the guy hundreds interior the compound Moles = grams/molar mass Molecules = moles x 6.023x10^23 molecules/mole Atoms = molecules x 6.023x10^23 atoms/molecule

Answer 3

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Answer 4

Dimensional Analysis = Stoichiometry

Problems 1,2
When converting grams to moles think Stoichiometry

1) (689.3g AlSO4 x 1 mole AlSO4) / molarmass AlSO4(g)
______Mole AlSO4=

As you see the grams cancel out and you are left with moles
Try number 2 if you know the concept now.

For Problems 3,4
When converting moles or atoms to grams think Stoichiometry!

3) (1.50 mole CaCl x molarMass(g) CaCl) / 1 mole CaCl
______Grams CaCl=

As you can see to get grams you also cancel out the moles

4) Formula units is another fancy name for molecules or atoms. A different process takes place, but its still Stoichiometry!

a) (1.26^26 Pu(particle units) x 1 mole) / 6.02^23 = molar value
b) (Molar value x molarMass(NaPO4)) / 1 mole = Grams "

You always want to cancel out the ones you don't want to get grams.

For Problems 5,6
@When converting moles or grams to particles think Stoichiometry!

5) (2.57 moles x 6.02^23) / 1mole = Anwser
The moles cancel out
6) a) (42.8 g x 1mole MgSO4) / Molar mass(MgSO4)
b) Answer form ax6.02^23 = answer