Molar Conversions
Your water bottle holds 18.0 g of water. How many moles of H₂O is that?
1 mole (18.0 g ÷ 18.02 g/mol)
Hydrogen gas reacts with oxygen gas to produce water. Write the balanced equation.
2H₂ + O₂ → 2H₂O
A rocket nerd is building a launch pad in his garage. In 2H₂ + O₂ → 2H₂O, he has 6 mol of H₂. How many moles of O₂ does he need before the neighbors call the fire department?
3 moles
You planned to bake 20 cookies for the bake sale, but you got distracted by your phone and burned half of them. What’s your percent yield?
50%. The “burnt” ones are now “extra crispy”, and you gave them to your brother(hopefully he doesn't get cancer)
How many light bulbs could you power for a day with the energy in a single banana?
A banana has about 100 Calories (roughly 420 kJ). A 10-watt LED bulb uses 864 kJ per day, so a banana powers one for about 12 hours.
A 0.500 g diamond is pure carbon. About how many carbon atoms are in it?
About 2.51 × 10²² atoms
(0.500 g ÷ 12.01 g/mol × 6.022 × 10²³)
Iron rusts when solid iron reacts with oxygen gas to form iron(III) oxide. Write the balanced equation.
4Fe + 3O₂ → 2Fe₂O₃
An airbag needs 70.0 L of N₂ at STP to save your face: 2NaN₃ → 2Na + 3N₂. How many grams of NaN₃ (65.01 g/mol) are in the bag?
Hint: 1 mole = 22.4L of gas
70.0 L ÷ 22.4 = 3.125 mol N₂, so 2.083 mol NaN₃, which is about 135 g
Your theoretical yield is 25.0 g of product, but you spilled some on the floor and said the five-second rule applies to chemistry. You collected 20.0 g. What’s your percent yield?
80.0%.
Which contains more individual particles: a teaspoon of water or all the grains of sand on a beach?
A teaspoon of water
If a 24K gold ring is worth $670, how many gold atoms are in it?
Gold market price today: $130/g
About 1.53 × 10²² atoms
$670 × 1g/$130 = 5g
5 g ÷ 196.97 g/mol × 6.022 × 10²³
A camping stove burns propane (C₃H₈) in oxygen, producing carbon dioxide and water vapor. Write the balanced equation.
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
Your dad is grilling and refuses to let anyone else touch the tongs. He burns 3.0 mol of propane: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. How many moles of CO₂ does he release while insisting the burgers are “almost done”?
9.0 mol
The burgers are not almost done.
2Mg + O₂ → 2MgO. A student burns 24.3 g of Mg (24.30 g/mol) for that blinding white flash, ignoring the teacher’s “don’t stare” warning, and now he's blind. What’s the theoretical yield of MgO (40.30 g/mol), and what’s the percent yield if he scrapes 36.3 g off the crucible?
Theoretical yield is 40.3 g (1.00 mol), so the percent yield is 36.3 ÷ 40.3 = 90.1%.
What part of the banana is slightly radioactive?
All of it! Since bananas contain potassium, it also has a bit of potassium-40, which is radioactive.
A can of soda has about 39 g of sucrose (C₁₂H₂₂O₁₁, 342.3 g/mol). How many moles of sucrose is that, and how many carbon atoms does it contain?
0.114 mol sucrose, about 8.23 × 10²³ carbon atoms (0.114 mol × 12 C per molecule × 6.022 × 10²³)
Aqueous calcium chloride is mixed with aqueous sodium phosphate. Solid calcium phosphate forms, and aqueous sodium chloride remains. Write the balanced equation.
3CaCl₂ + 2Na₃PO₄ → Ca₃(PO₄)₂ + 6NaCl
A movie villain is planning a dramatic metal-melting scene using thermite: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe.
How many grams of aluminum (26.98 g/mol) does he need to react completely with 80.0 g of Fe₂O₃ (159.7 g/mol)?
0.501 mol Fe₂O₃ needs 1.00 mol Al, which is 27.0 g
Dad’s grill burns 44.1 g of propane (C₃H₈, 44.10 g/mol) while he explains why he doesn’t need a thermometer. How many grams of CO₂ and H₂O form, and how many grams of O₂ got eaten?
C3H8 + 5O2 → 3CO2 + 4H2O
44.1g of propane × 1 mol/44.1g = 1 mole of propane
1.00 mol propane produces 3.00 mol CO₂ (132 g) and 4.00 mol H₂O (72.1 g) and consumes 5.00 mol O₂ (160 g).
If you took all of the iron in your body and made a nail, how long would the nail be? (in inches)
3 in.
A balloon holds 5.60 L of CO₂ (dry ice vapor) at STP. What is the mass of the gas, and how many oxygen atoms are inside?
Hint: 1 mole = 22.4L of gas
5.60 L ÷ 22.4 L/mol = 0.250 mol
Oxygen atoms: 0.250 mol × 2 × 6.022 × 10²³ ≈ 3.01 × 10²³
Gasoline is mostly octane (C₈H₁₈). Write the balanced equation for its complete combustion using the smallest whole-number coefficients.
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
A science fair kid wants first place and has a baking soda volcano to get it: NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂. He uses 8.40 g of NaHCO₃ (84.01 g/mol).
How many grams of CO₂ gas does the “eruption” produce, and what volume is that at STP? (The judges are unimpressed either way.)
0.100 mol NaHCO₃ produces 0.100 mol CO₂, which is 4.40 g and 2.24L
Unfortunately, the volcano was too small, so he got a participation medal. :(
C₇H₆O₃ (salicylic acid, 138.12 g/mol) + C₄H₆O₃ → C₉H₈O₄ (aspirin, 180.16 g/mol) + C₂H₄O₂. A student starts with 2.00 g of salicylic acid and collects 2.10 g of aspirin, then needs one for the headache from calculating the yield. What’s the percent yield?
2.00 g ÷ 138.12 = 0.01448 mol, so the theoretical yield is 2.61 g
Percent yield is 2.10 ÷ 2.61 = 80.5%.
The student is gonna take the aspirin bc of this problem
How many diamonds could you make from your body’s carbon if each is one carat (0.2 g)?
About 63,000