Exam #2 General Chemistry 1 USF exam questions and 100% correct answers 2025

Exam #2 General Chemistry 1 USF
Molecular Mass (Beginning of Ch. 3) - ✔✔ correct answer The atomic masses of all atoms in a
molecule.



Ex: O2, H2, Na, etc.



Formula Mass - ✔✔ correct answer The atomic masses of all atoms in a formula unit of a compound,
whether molecule or not (ionic bonds).



Ex: Ca(OH)2, CH3NH2, etc.



Avagadro's Number - ✔✔ correct answer Number of atoms in 12g of carbon-12

6.02 x 10^23



Percent Composotion - ✔✔ correct answer Mass percentage of each element in the compound.



Determining Mass Percentage: - ✔✔ correct answer 1. Find the molar mass of each molecule



2. Divide the mass of each by the total mass combined



3. Multiply by 100



Empirical Formula (simplest) - ✔✔ correct answer Formula of a substance written with the smallest
subscripts.



Determining Empirical Formula - ✔✔ correct answer 1. Start with percent composition

Assume 100g so 100g = 100%



2. Convert from g to moles for each element.



3. Manipulate the mole ratios by dividing each mole by the smallest one.

*If the result isn't a whole number, MAKE IT ONE*

- Ex: if decimal portion is 0.5, multiply x2, etc.

,Exam #2 General Chemistry 1 USF

Molecular Formula - ✔✔ correct answer Formula for a molecule in which subscripts are whole-
numbers

(Multiply the subscript of the empirical formula)



Determining Molecular Formula - ✔✔ correct answer 1. Find empirical formula weight



2. Find ratio of molecular weight to empirical formula weight

*n= molecular weight / empirical formula weight*



3. Multiply each subscript of the empirical formula by n



Stoichometry (railroad tracks) - ✔✔ correct answer Calculation of the reactants and products in a
chemical reaction.



g given -> moles given -> moles wanted -> g wanted



Understanding a Chemical Equation - ✔✔ correct answer The coefficients of a balanced chemical
equation may be interrupted by a number of molecules or number of moles, depends on its needs.



Chemical Equation Rules - ✔✔ correct answer 1. Order of charges is + first, then -



2. Anything + O2 -> CO2 + H2O



3. H2O never splits.

Ex: NaCl + H2O -> Na^+ + Cl^- + H2O



Finding B with the amount of A given: - ✔✔ correct answer 1. Convert from grams of A to moles of A

• Use A's molar mass



2. Convert from moles of A to moles of B

• 1 mol A / 1 mol B- BRIDGE

, Exam #2 General Chemistry 1 USF

3. Convert from moles of B to grams of B

• Use B's molar mass



Limiting Reactant - ✔✔ correct answer - The reactant that is completely consumed when a reaction
is complete (smallest)



- When the reactant is fully consumed, the reaction stops



- It is a limiting reactant problem IF there is more than one reactant.



- All amounts of product are determined by the limiting reactant.



Determining Limiting Reactant - ✔✔ correct answer 1. Use each given amount to calculate the
amount of product made for each



2. The limiting reactant will produce the smaller number of product



Electrolyte (Beginning of Ch. 4) - ✔✔ correct answer - Dissolves to produce Ions

- Ions are moving charges that complete a circuit (lightbulb circuit)



Strong Electrolyte - ✔✔ correct answer Exists in a solution almost entirely as ions.



Weak Electrolyte - ✔✔ correct answer Dissolves in water to give a small number of ions. (Weak light
bulb)



Soluble - ✔✔ correct answer Compounds that dissolve.



Insoluble - ✔✔ correct answer Compounds that dissolve very little or not at all.



Molecular Equation - ✔✔ correct answer Reactants and products written as molecular substances
(s), (l), (g), (aq).