Chapter 12 - Stoichiometry Flashcards
Chemical reactions can be described in terms of what quantities?
A balanced chemical equation can be interpreted in terms of #’s of atoms, molecules, or moles; mass; and volume.
How do chemists use balanced equations?
Chemists use balanced chemical equation as a basis to calculate how much reactant is needed or how much product will be formed in a reaction.
Define Stoichiometry.
The calculation of quantities in chemical reactions.
How are mole ratios used in chemical calculations?
Mole ratios are used to convert b/w a given # of moles of reactant/product to moles of a different reactant/product.
What’s a mole ratio?
A conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles.
Outline the sequence of steps needed to solve a typical stoichiometric problem.
1) Given quantity is first converted to moles.
2) Mole ratio from balanced equation is used to calculate the # of moles of wanted substance.
3) Moles are converted to any other unit of measurement related to unit mole.
What’s the difference b/w the limiting reagent and the excess reagent.
Limiting reagent: reactant that determines the amount of product that can be formed by a reaction.
Excess reagent: reactant that is not completely used up in a reaction.
State the difference b/w theoretical yield, actual yield, and percent yield.
▪️Theoretical yield: maximum amount of product that could be formed from given amounts of reactants.
▪️Actual yield: amount of product that actually forms when reaction is carried out in the lab.
▪️Percent yield: ratio of the actual yield to the theoretical yield as a percent. Percent yield = (AY/TY)x100%
How does an insufficient quantity of a reactant affect the amount of product formed?
An insufficient quantity of any reactant will limits the amount of product that forms.
What does the percent yield measures?
It measures the efficiency of a reaction carried out in the lab.
What quantities are always conserved in chemical equations?
Mass and atoms.
Interpret the given equation in terms of # of molecules, # of moles, and masses of reactants and products.
2K + 2H2O —> 2KOH + H2
▪️# of molecules: 2 molecules of K + 2 molecules of H2O —> 2 molecules of KOH + 1 molecule of H2
▪️# of moles = same as molecules
▪️Masses of reactants and products:
39 g of K + 36 g of 2H2O —> 112 g of 2KOH + 2 g of H2
Balance this equation:
C2H5OH + O2 —> CO2 + H2O
C2H5OH + 3O2 —> 2CO2 + 3H2O
Practice #23 pg. 398 #37 & #38 pg. 408
Okay.
