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Stoichiometry

Definition

Stoichiometry involves calculations based on balanced chemical equations regarding quantities involved in chemical reactions - both reactants and products.

Analogy

Think of stoichiometry like a recipe. If you know how many cookies one recipe makes, you can figure out how much of each ingredient you'd need to make more or fewer cookies. In chemistry, if we know the balanced equation for a reaction (our "recipe"), we can calculate how much of any reactant is needed to produce a certain amount of product.

Related terms

Mole Ratio: The ratio between the amounts in moles of any two compounds involved in a chemical reaction.

Limiting Reactant: The substance that is totally consumed when the chemical reaction is complete.

Excess Reactant: The reactants present in quantities greater than necessary to react with the quantity of the limiting reagent.

"Stoichiometry" appears in:

Practice Questions (6)

  • Which of the following is true about the relationship between the amount of substance produced during electrolysis and the stoichiometry of the reaction?
  • Faraday’s laws can be used to determine the stoichiometry of the redox reaction occurring in an electrochemical cell with respect to ALL of the following, EXCEPT for:
  • Faraday’s laws can be used to determine the stoichiometry of the redox reaction occurring in an electrochemical cell with respect to ALL of the following, EXCEPT for:
  • Faraday’s laws can be used to determine the stoichiometry of the redox reaction occurring in an electrochemical cell with respect to ALL of the following, EXCEPT for:
  • Why does stoichiometry play an important role in finding the concentration or partial pressure of a species at equilibrium?
  • To solve this problem, we need to use the balanced chemical equation for the reaction between HCl and NaOH, which is HCl + NaOH → NaCl + H2O. We can see from the equation that the stoichiometry is 1:1, meaning that 1 mole of HCl reacts with 1 mole of NaOH. Therefore, the number of moles of HCl needed is equal to the number of moles of NaOH given. We can use the formula M = moles/volume to find the volume of the HCl solution needed. Rearranging the formula, we get volume = moles/M. Plugging in the values, we get volume = 0.150 mol / 0.200 M = 0.750 L. Since we have 25mL of NaOH, we need to multiply 0.750 L by 25 mL NaOH /1000 mL. Therefore, the answer is 0.01875 L = 18.75 mL.


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AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.