Practice Worked Practice Problems (1.5) - Unit 1: Stoichiometric Relationships

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6 sample questions

Question 1.
Calculate the number of moles in 50.0 g of sodium chloride (NaCl).
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Use the number of moles = mass / molar mass.
Question 2.
What is the molar mass of calcium carbonate (CaCO₃)?
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Add the atomic masses of Ca, C, and O.
3Question 3.
What is Avogadro's number?
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This number is the bridge between microscopic and macroscopic amounts.
4Question 4.
A limiting reagent is defined as:
- The reagent in excess
- The reagent that is completely consumed
- The catalyst in a reaction
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Think about the reagent that runs out first in a chemical reaction.
Question 5.
You have 10.0 g of magnesium and 50.0 g of O₂. Determine the limiting reagent and calculate the theoretical yield of MgO.
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Start by writing the balanced equation: 2 Mg + O₂ → 2 MgO.
Question 6.
A solution contains 5 g of NaCl in 250 mL. How many moles of NaCl are in the solution? If you dilute this solution to 500 mL, what is the new molarity?
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Molarity = moles of solute / liters of solution.

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