Stoichiometry Basics
Before starting any stoichiometry calculation, what must you do first?
A. Convert to grams
B. Identify limiting reagent
C. Balance the equation
D. Find percent yield
C. Balance the equation
What color does phenolphthalein turn at the endpoint?
A: Pink
What type of reaction produces a solid when two aqueous solutions are mixed?
A: Precipitation reaction.
According to Brønsted–Lowry, what is an acid?
A: A proton donor.
According to the stoichiometry map, what unit should you always convert the “given” into first?
A: Moles
Name the three main types of titrations.
A: Acid-base, redox, and precipitation titrations.
What is usually released in combustion reaction
Co2 and H2O
Identify the reduction and oxidation in this reaction
4Fe(s)+3O2 ->2Fe2O3
Fe is oxidized and O is reduced.
Define mole ratio and why it is important
Conversion factor between reactants and products in a balanced reaction and they help chemists calculate almost the exact amount needed when they work in a lab.
Name one common acid-base indicator used in lab.
A: Phenolphthalein (also bromothymol blue, methyl red, etc.)
When does a single replacement reaction not take place?
The free element is less electro negative than the compound.
According to the Brønsted–Lowry definition, identify the acid, base, conjugate acid, and conjugate base in the reaction below:
NH3+H2O→NH4+ + OH−
Answer:
Acid: H₂O (donates H⁺)
Base: NH₃ (accepts H⁺)
Conjugate acid: NH₄⁺
Conjugate base: OH⁻
How many grams of H₂O are produced from 1.0 g of H₂O₂? (Reaction: 2H₂O₂ → 2H₂O + O₂)
A: 0.53 g of H₂O
Which type of titration involves electron transfer?
A: Redox titration
Predict whether a precipitate forms when Na₂SO₄(aq) reacts with BaCl₂(aq).
If so, name it.
A:
Yes — BaSO₄(s) precipitate forms.
What is an amphiprotic substance?
A: A substance that can act as both an acid and a base.
Mg + 2HCL -> MgCl2 + H2
4.00 grams of Mg react with 45 grams of HCL.
Identify the limiting reactant
Mg is the limiting reactant
An Acid-base titration usually relies on...
pH changes and color indicator
A student predicts that the reaction below is a redox reaction:
NaCl(aq)+AgNO3(aq)→AgCl(s)+NaNO3(aq)
Give one reason why this reaction is NOT a redox reaction, even though a visible change occurs.
No electrons are transferred
Oxidation numbers of all elements remain unchanged
The reaction is a double-replacement precipitation reaction
The visible change (solid formation) is due to insolubility, not electron transfer
2Al + 3Cu2+ → 2Al3+ + 3Cu
Determine the total number of electrons transferred in the reaction
6 electrons