mole problems

Round all masses to the 10ths place

Step One: two atoms of iron and three of oxygen

Step Two: Fe = 55.8 amu and O = 16.0 amu

Step Three: (2 x 55.8) + (3 x 16.0)

Step Four: 111.6 + 48.0 = 159.6 amu (grams) for one mole

Step One: one atom of potassium, one of chlorine, and four of oxygen.

Step Two: K = 39.1 amu, Cl = 35.5 amu, O = 16.0 amu

Step Three: (1 x 39.1) + (1 x 35.5) + (4 x 16.0)

Step Four: 39.1 + 35.5 + 64.0 = 138.6 amu (grams) for one mole

Step One: two atoms of nitrogen, eight of hydrogen and one of sulfur

Step Two: N = 14.0 amu, H = 1.0 amu, S = 32.1 amu

Step Three: (2 x 14.0) + (8 x 1.0) + (1 x 32.1)

Step Four: 28 + 8.0 + 32.1 = 68.1 amu (grams) for one mole

Calculate the molar mass of Al(NO3)3

Al(1 x 27.0) + N(3 x 14.0) + O(9 x 16.0) =

213.0 amu (grams) is the mass of one mole of aluminum nitrate.

1. AlCl3 2. Ba(SCN)2 3. LiH 4. Ba(BrO3)2 5. AlBr3 6. HCl

1. 133.5 g/mol 2. 253.5 g/mol 3. 7.9 g/mol 4. 393.1 g/mol 5. 266.7 g/mol 6. 36.5 g/mol

Round all final answers to 3 sig figs

KMnO4 = 158.0 g / mole of KMnO4

Now let’s solve it

25.0 g x 1 mole = 0.158191804 moles 158.0 g

0.158 moles

H2O2 = 34.0 g / mole

Now, let’s solve it

17.0 g x 1 mol H2O2 = 0.5 moles

34.0 g

0.500 moles

Calculate the moles present in: 1) 2.00 grams of H2O 2) 75.57 grams of KBr 3) 100. grams of KClO4

4) 8.76 grams of NaOH 5) 0.750 grams of Na2CO3

Remember to round answers to 3 sig figs

1) 0.111 moles 2) 0.635 moles 3) 0.722 moles 4) 0.219 moles 5) 0.00708 moles

Round all answers to 3 sig figs

H2O2 molar mass = 34.0 grams/mole

0.700 moles x 34.0 grams = 23.8 g 1 mole

23.8 grams

KClO3 molecular mass = 122.6 g/mole

2.50 moles x 122.6 g = 306.5 grams 1 mole

307 grams

Calculate the grams present in: 1) 0.200 moles of H2S 2) 0.100 moles of KI 3) 1.500 moles of KClO 4) 0.750 moles of NaOH 5) 3.40 x 10-5 moles of Na2CO3

Remember to round answer to 3 sig figs

1) 6.82 grams 2) 16.6 grams 3) 136 grams 4) 30.0 grams 5) 0.00360 grams

6.02 x 1023 particles = 1 mole

Particles can mean atoms or molecules

One mole of donuts contains 6.02 x 1023 donuts

One mole of H2O contains 6.02 x 1023 molecules

One mole of nails contains 6.02 x 1023 nails

One mole of Fe contains 6.02 x 1023 atoms

One mole of dogs contains 6.02 x 1023 dogs

One mole of electrons contains 6.02 x 1023 electrons

One mole of Chemistry students contains 6.02 x 1023 poor, suffering (I mean happy, joyful) high school students

0.450 mole Fe x 6.02 x 1023 atoms1 mole

= 2.709x1023 atoms

Final, rounded answer: 2.71x1023 atoms

0.200 mole x 6.02 x 1023 atoms1 mole

= 1.204x1023 atoms

Final, rounded answer: 1.20x1023 atoms

1) Calculate the number of molecules in 1.058 mole of H2O

2) Calculate the number of atoms in 0.750 mole of Fe

Remember to round to 3 sig figs

1) 6.37x1023 molecules

2) 4.52x1023 atoms

Grams to particles OR particles to grams

Grams to atoms OR atoms to grams

If MOLE is not stated, it’s a two step problem

ROUND ALL ANSWERS TO # SIG FIGS

0.450 g x 1 mole Fe x 6.02x1023 atoms =

55.8 g 1 mole

4.8548387x1021 atoms

Final answer = 4.85x1021 atoms

H2O molecular mass = 18.0 g

0.200 g x 1 mole H2O x 6.02x1023 molecules

18.0 g 1 mole

6.6838888889x1021 molecules

Final answer = 6.68x1021 molecules

1) Calculate the number of molecules in 1.058 gram of H2O

2) Calculate the number of atoms in 0.750 gram of Fe

Remember to round answer to 3 sig figs

1) 3.54x1022 molecules

2) 8.10x1021 atoms