divide by molar mass
🧮ACS GENERAL CHEMISTRY STUDY GUIDE
Moles and Stoichiometry for the ACS Exam
Practice molar mass, formula calculations, limiting reactants, yields, combustion data, and solution stoichiometry.
8 key ideas8 flashcards5 practice questions
Copy to my workspace →LISTEN WITH SOBATake this set with you.
Audio is saved on this device after the first play.
Cross through moles before moving between substances.
use the balanced equation
multiply by molar mass
Key ideas to know
Start with the relationships between ideas. Then close the notes and explain each one from memory.
- 01
One mole contains the Avogadro number of specified particles.
- 02
Molar mass converts between a substance's mass and amount in moles.
- 03
A balanced equation gives mole ratios, not direct mass ratios.
- 04
The limiting reactant is consumed first and sets the maximum product amount.
- 05
Theoretical yield comes from stoichiometry, while actual yield comes from measurement.
- 06
Percent yield equals actual yield divided by theoretical yield times one hundred.
- 07
An empirical formula gives the smallest whole-number atom ratio.
- 08
Combustion data can determine carbon and hydrogen amounts from carbon dioxide and water products.
PART OF THE ACS GENERAL CHEMISTRY GUIDE
See every set in this course and follow a focused review order.
Open the full ACS General Chemistry guide →Two ideas worth correcting now
NOT QUITE
→The reactant with the smaller mass is limiting
USE THIS INSTEAD
The limiting reactant depends on moles and the balanced ratio.
NOT QUITE
→Coefficients alter chemical formulas
USE THIS INSTEAD
Balancing alters only coefficients, never subscripts within a formula.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1What is Avogadro's number?Show answer ＋
Approximately 6.022 × 10²³ particles per mole.
2What does a balanced coefficient ratio compare?Show answer ＋
Moles of reactants and products.
3How is a limiting reactant found?Show answer ＋
Calculate product from each reactant; the smaller product amount identifies the limit.
4What is excess reactant?Show answer ＋
Reactant left after the limiting reactant is consumed.
5What is theoretical yield?Show answer ＋
The maximum product predicted from the limiting reactant.
6How do you obtain an empirical formula from percentages?Show answer ＋
Assume a mass basis, convert each element to moles, divide by the smallest amount, then reach whole numbers.
7What does molarity equal?Show answer ＋
Moles of solute divided by liters of solution.
8Why must units stay attached during conversion?Show answer ＋
They show which factors cancel and expose an inverted ratio.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01How many moles are in 18.0 g of water?
Divide 18.0 g by water's molar mass, about 18.0 g/mol, to obtain about 1.00 mol.
02Why can a balanced equation not be used as a gram ratio?
Coefficients count particles or moles, and different substances have different molar masses.
03How do you find leftover excess reactant?
Use the limiting reactant to calculate how much excess reactant reacts, then subtract from the starting amount.
04How can a hydrate formula be found after heating?
Find moles of anhydrous salt and moles of water lost, then reduce their ratio to whole numbers.
05Why can percent yield exceed one hundred?
The product can contain solvent, water, impurities, or measurement error, so measured mass is too high.
Related study materials
〜•‿•
Ready to remember this?
Copy the set and let Soba schedule what to review next.
Study this set for free →