NEXPHYRA / EXAM STUDY PACK
Stoichiometry
NEXPHYRA / EXAM STUDY PACK
Mole ratios, limiting reactants, and yield
Use the balanced reaction as a conversion map. Track what reacts, what remains, and what can actually be
collected.
MODEL CALCULATE VERIFY
Balance atoms and charge 4 worked examples + 12 original Unit cancellation, limiting checks
problems and detailed solutions
A focused algebra-based review for upper high school and introductory college chemistry. All numerical
exercises state their assumptions. Reaction calculations describe idealized quantities, not experimental
instructions.
US Letter • English • Static PDF • Personal study use
Edition 2 | Work in moles between chemical species; convert to mass only after the ratio step.
Stoichiometry
,NEXPHYRA / EXAM STUDY PACK
Quick Start and Contents
If you memorize one route, use this: given quantity → moles of given species → balanced coefficient ratio →
moles of target → requested unit. With several reactants, compare how much product each could make before
choosing a limiting reactant.
Pages Topic
3-4 Balanced reactions, limiting reactants and quantity maps
5-8 Formula sheet, symbols, units and formula cards
9 Method and mistakes
10-11 Four worked examples
12-14 Twelve practice problems
15-18 Detailed solutions
19 Checklist and sources
20 Final one-page review
Study route
• First pass: identify each species and circle the requested unit. Write the balanced equation before any ratios.
• Practice pass: solve P1-P4, then P5-P8, then P9-P12. Read a solution only after recording your setup.
• Final pass: check leftover reactant amounts and whether an actual yield is consistent with a theoretical
maximum.
Unless a problem says otherwise, model the specified reaction as complete with no competing reaction, and
use the molar masses stated in that problem. A balanced equation alone does not prove that a reaction is fast
or complete.
Stoichiometry
, NEXPHYRA / EXAM STUDY PACK
A Balanced Reaction Is a Ratio
Chemical formulas identify substances. Coefficients count reaction proportions. Changing a subscript changes
the substance; changing a coefficient changes how much of it participates. Balance each element and total
electric charge, using the smallest whole-number coefficients for presentation.
Example of a chemical counting statement
N2 + 3 H2 → 2 NH3 means one mole of N2 reacts with three moles of H2 to form two moles of NH3, if this is the
only reaction and the stated amount reacts. It does not mean one gram reacts with three grams.
1. GIVEN QUANTITY 2. MOLES OF GIVEN 3. BALANCED RATIO
m, cV, or N convert to mol target / given
Coefficients 5. REQUESTED UNIT 4. MOLES OF TARGET
connect moles. m, V, or entities apply mole ratio
Use the amount that actually reacts; if several reactants are given, identify the limiting reactant before predicting product.
Given Convert first Then use
Mass of reactant n = m/M Mole ratio from the balanced equation
Solution amount n = cV Mole ratio; use final solution volume
Entity count n = N/NA Mole ratio for the correct entities
Several reactants Moles of each divided by its Smallest available reaction amount
coefficient
Collected product Compare with theoretical product Percent yield
Theoretical yield is the maximum predicted by the stated stoichiometric model and available reactants. Actual
yield is a measured amount of the specified product. Impurities, incomplete reaction, side reactions and
handling losses can make them differ.
Stoichiometry
Stoichiometry
NEXPHYRA / EXAM STUDY PACK
Mole ratios, limiting reactants, and yield
Use the balanced reaction as a conversion map. Track what reacts, what remains, and what can actually be
collected.
MODEL CALCULATE VERIFY
Balance atoms and charge 4 worked examples + 12 original Unit cancellation, limiting checks
problems and detailed solutions
A focused algebra-based review for upper high school and introductory college chemistry. All numerical
exercises state their assumptions. Reaction calculations describe idealized quantities, not experimental
instructions.
US Letter • English • Static PDF • Personal study use
Edition 2 | Work in moles between chemical species; convert to mass only after the ratio step.
Stoichiometry
,NEXPHYRA / EXAM STUDY PACK
Quick Start and Contents
If you memorize one route, use this: given quantity → moles of given species → balanced coefficient ratio →
moles of target → requested unit. With several reactants, compare how much product each could make before
choosing a limiting reactant.
Pages Topic
3-4 Balanced reactions, limiting reactants and quantity maps
5-8 Formula sheet, symbols, units and formula cards
9 Method and mistakes
10-11 Four worked examples
12-14 Twelve practice problems
15-18 Detailed solutions
19 Checklist and sources
20 Final one-page review
Study route
• First pass: identify each species and circle the requested unit. Write the balanced equation before any ratios.
• Practice pass: solve P1-P4, then P5-P8, then P9-P12. Read a solution only after recording your setup.
• Final pass: check leftover reactant amounts and whether an actual yield is consistent with a theoretical
maximum.
Unless a problem says otherwise, model the specified reaction as complete with no competing reaction, and
use the molar masses stated in that problem. A balanced equation alone does not prove that a reaction is fast
or complete.
Stoichiometry
, NEXPHYRA / EXAM STUDY PACK
A Balanced Reaction Is a Ratio
Chemical formulas identify substances. Coefficients count reaction proportions. Changing a subscript changes
the substance; changing a coefficient changes how much of it participates. Balance each element and total
electric charge, using the smallest whole-number coefficients for presentation.
Example of a chemical counting statement
N2 + 3 H2 → 2 NH3 means one mole of N2 reacts with three moles of H2 to form two moles of NH3, if this is the
only reaction and the stated amount reacts. It does not mean one gram reacts with three grams.
1. GIVEN QUANTITY 2. MOLES OF GIVEN 3. BALANCED RATIO
m, cV, or N convert to mol target / given
Coefficients 5. REQUESTED UNIT 4. MOLES OF TARGET
connect moles. m, V, or entities apply mole ratio
Use the amount that actually reacts; if several reactants are given, identify the limiting reactant before predicting product.
Given Convert first Then use
Mass of reactant n = m/M Mole ratio from the balanced equation
Solution amount n = cV Mole ratio; use final solution volume
Entity count n = N/NA Mole ratio for the correct entities
Several reactants Moles of each divided by its Smallest available reaction amount
coefficient
Collected product Compare with theoretical product Percent yield
Theoretical yield is the maximum predicted by the stated stoichiometric model and available reactants. Actual
yield is a measured amount of the specified product. Impurities, incomplete reaction, side reactions and
handling losses can make them differ.
Stoichiometry
