Stoichiometry
What is the first step when solving a stoichiometry problem from a chemical equation?
Make sure the equation is balanced
What does an empirical formula represent?
The simplest whole-number ratio of atoms in a compound.
Name NaCl
Sodium chloride
What unit connects grams to particles in the usual conversion pathway?
(To go from grams to number of particles you need to go through another unit first, what is it)
Moles
How many significant figures are in 0.00450?
3 sig figs
How many moles are in 182.0 g of H₂O?
10.10 mol H₂O
A compound contains 2.0 mol C and 4.0 mol H. What is its empirical formula?
CH₂
Write the formula for magnesium chloride
MgCl₂
What is the usual pathway for converting grams of A to grams of B in a reaction?
grams A → moles A → moles B → grams B.
Calculate and report the answer with the correct number of significant figures: 12.5 × 2.0
25
How many grams are in 2.00 mol CO₂?
88.0 g CO₂
A compound is 40.0% C, 6.7% H, and 53.3% O. What is its empirical formula? Hint: Assign a mass (g) to the compound
CH₂O
Name Ca(NO₃)₂
Calcium nitrate
What is the key naming difference between ionic and molecular compounds? Explain in your own words.
Ionic compounds use ions/charges; molecular compounds use prefixes
Calculate and report the answer with the correct number of significant figures: 15.67 + 2.3
18.0
For H₂ + O₂ → H₂O, how many moles of H₂O can form from 3.00 mol H₂ and 4.00 mol O₂
3.00 mol H₂O
Why do you divide all mole amounts by the smallest mole amount?
To turn the amounts into the simplest relative ratio.
Write the formula for aluminum oxide
Al₂O₃
A student writes CaCl for calcium chloride.What mistake did they make and why is it a mistake?
Charge neutrality: Ca²⁺ needs two Cl⁻, so CaCl₂
Calculate and report the answer with the correct number of significant figures: (4.25 × 2.0) ÷ 3.00
2.8
For N₂ + H₂ → NH₃, how many moles of NH₃ can form from 4.00 mol N₂ and 4.00 mol H₂
8.00 mol NH₃
A compound has 0.50 mol C, 0.75 mol H, and 0.25 mol O. What is the empirical formula?
C₂H₃O
Name N₂O₅. Is it ionic or molecular?
Dinitrogen pentoxide; molecular
A student gets an empirical-formula ratio of 1 : 1.5 : 1, what should they do in order to obtain the empirical formula?
Multiply all ratios by 2 → 2 : 3 : 2.
Calculate and report the answer with the correct number of significant figures: [(3.45 × 2.0) + 1.25] ÷ 2.5
3.3