Calculate the mass (in grams) of each sample. 3.9×10 25 O3 molecules 4.46×10 19

Question

Calculate the mass (in grams) of each sample.

3.9×1025 O3 molecules

4.46×1019 CCl2F2 molecules

9 water molecule(s)

Determine the number of moles of oxygen atoms in each of the following.

2.28×102 mol H2CO3

Give the name from the formula or the formula from the name for each of the following hydrated ionic compounds.

Zn3(PO4)23H2O

iridium(III) bromide tetrahydrate

BeCrO45H2O

aluminum nitrate dihydrate

What mass (in grams) of iron(III) oxide contains 67.3 g of iron? Iron(III) oxide is 69.94% iron by mass.

Explanation / Answer

(1) 3.9×1025 O3 molecules

1 mol -------------------> 6.023 x 10^23 molecules

x moles ---------------> 3.9×1025 O3 molecules

x = 3.9×1025 / 6.023 x 10^23

x = 64.75 moles

mole = mass / molar mass

64.75 = mass / 48

mass = 3108 g

(2) 4.46×1019 CCl2F2 molecules

moles = 4.46×1019 / 6.023 ×1023

moles = 7.4 x 10^-5

CF2Cl2 molar mass = 121 g /mol

mass =    121 x 7.4 x 10^-5 = 8.95 x 10^-3 g

(3)   9 water molecule(s)

1mol ----------------------> 6.023 x 10^23 molecules

x ---------------------------> 9 water molecules

x = 9 / 6.023 x 10^23

   = 1.9 x 10^-23

mass = 18 x 1.9 x 10^-23

            = 2.69 x 10^-22 g

(4) Zn3(PO4)23H2O --------------------> zinc phosphate trihydrate

(5) iridium(III) bromide tetrahydrate ---------------------> IrBr3.4H2O

(6) BeCrO45H2O ----------------------------> Berillium Chromate pentahydrate

(7) aluminum nitrate dihydrate ----------------> Al(NO3)2 .2H2O

(8 ) What mass (in grams) of iron(III) oxide contains 67.3 g of iron? Iron(III) oxide is 69.94% iron by mass

     Fe2O3

Fe mass % = (Fe mass / total mass ) x 100

69.94 = (67.3 / total mass) x100

total mass = 96.2 g

mass of Fe(III) oxide = 96.2 g

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