Stoichiometry Problems

Consider the reaction of magnesium hydroxide with phosphoric acid. 3Mg(OH)2 + 2H3PO4 H Mg3(PO4)2 + 6H2O (a) Calculate the mass of Mg3(PO4)2 that will be formed (assuming a 100% yield) from the reaction of 45.0 g of 92.5% Mg(OH)2 with an excess of H3PO4

• 6.97 g Mg₃(PO₄)₂

• 20.9 g Mg₃(PO₄)₂

• 62.7 g Mg₃(PO₄)₂

• 1.39 g Mg₃(PO₄)₂

Tags

NGSS.HS-PS1-7

CH₄ + 2 O₂ → CO₂ + 2 H₂O
How many moles of carbon dioxide are produced from the combustion of 110 g of CH₄?

• 13.7 mol

• 2.75 mol

• 6.11 mol

• 6.85 mol

Calculate the mass (in g) of water produced from the complete combustion of 1.000 gallon (3.800 L) of gasoline (C₈H₁₈). The density of gasoline is 0.7900 g/mL.

• 8.522 X 10³ g H₂O

• 4.261 X 10³ g H₂O

• 9.737 X 10⁵ g H₂O

• 7.678 X 10³ g H₂O

Tags

NGSS.HS-PS1-7

What is the first step on solving stoichiometry problems?

• balance the chemical reaction

• unbalance the chemical reaction

• start solving by writing what is given

• panic, it really helps

How many grams of H₂O will be produced if I have 90 grams of O₂?

What is the first step to solve it?

• start with the mass of O₂

• start with the mass of H₂O

• start with the mole of H₂O

• start with the mole of O₂

How many grams of H₂O will be produced if I have 90 grams of O₂? Now that we got the mole of O₂. What is the next step to solve it?

• convert mole of H₂O to mass of H₂O

• convert mole of O₂ to mass of O₂

• convert mole of H₂O to mole of O₂

• convert mole of O₂ to mole of H₂O

To convert mole of O₂ to mole of H₂O, what stoichiometric ratio should be used?

• 2 mol H₂ : 2 mol H₂O

• 2 mol H₂O : 1 mol O₂

• 2 mol H₂ : 1 mol O₂

Tags

NGSS.HS-PS1-7

How many grams of H₂O will be produced if I have 90 grams of O₂? What is the next step to solve it?

• convert mass of H₂O to mole of H₂O

• convert mass of O₂ to mole of O₂

• convert mass of H₂O to mole of O₂

• convert mass of O₂ to mole of H₂O

How many grams of H₂O will be produced if I have 90 grams of O₂? Now that we got the mole of H₂O What is the last step to solve it?

• convert mole of H₂O to mass of H₂O

• convert mole of O₂ to mass of O₂

• convert mole of H₂O to mole of O₂

• convert mole of O₂ to mole of H₂O

Tags

NGSS.HS-PS1-7

How many moles of water are produced form 19.2 g of B₂H₆? How should we solve it?

• mole H₂O → mole of B₂H₆ → mass B₂H₆

• mass of B₂H₆ → mole B₂H₆ → mole H₂O

• mass of B₂H₆ → mole H₂O → mole B₂H₆ → mass H₂O

• mass of B₂H₆ → mole B₂H₆ → mole H₂O → mass H₂O