Step-by-Step Guidance for General Chemistry 1 Midterm Study Prep public

Notes Practice Video lessons

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Q1. If 1.85×10–3 moles of a hormone weigh 0.581 grams, calculate the molar mass of the hormone.

Background

Topic: Calculating Molar Mass

This question tests your ability to determine the molar mass of a substance using the mass and number of moles.

Key formula:

Step-by-Step Guidance

Identify the mass of the hormone: grams.
Identify the number of moles: moles.
Set up the formula for molar mass: .
Plug in the values, but do not calculate the final result yet.

Try solving on your own before revealing the answer!

Q2. Calculate the number of P atoms in 2.63 g of phosphorus pentabromide (PBr5). Calculate the mass in grams of Br in 3.28 x 1021 molecules of PBr5.

Background

Topic: Mole Concept

This question tests your understanding of converting between mass, moles, molecules, and atoms for a compound.

Key formulas:

Step-by-Step Guidance

Find the molar mass of PBr5 by adding the atomic masses of P and Br (5 times).
Calculate the moles of PBr5 in 2.63 g using .
Determine the number of molecules using Avogadro's number.
Calculate the number of P atoms by multiplying the number of molecules by 1 (since each molecule has 1 P atom).
For the second part, use the given number of molecules to find the number of Br atoms (multiply by 5), then calculate the mass of Br.

Try solving on your own before revealing the answer!

Q3. At equilibrium, the following decomposition reaction has 2.38 g NaNO3, 3.92 g NaNO2, and 1.29 g O2. 2 NaNO3 (s) → 2 NaNO2 (s) + O2 (g). How much in grams of NaNO3 is there originally if it is the only substance at the start of the reaction?

Background

Topic: Law of Conservation of Mass

This question tests your understanding of mass conservation in chemical reactions.

Key concept:

The total mass of reactants equals the total mass of products.

Step-by-Step Guidance

Sum the masses of all products: remaining.
Recognize that the original mass of NaNO3 is equal to the total mass of products.
Set up the equation: .
Plug in the values, but do not calculate the final result yet.

Try solving on your own before revealing the answer!

Q4. Identify the number of Al, S, and O atoms in the coagulating agent aluminum sulfate (Al2(SO4)3).

Background

Topic: Law of Definite Proportions

This question tests your ability to count atoms in a chemical formula.

Key concept:

Use subscripts and coefficients in the formula to determine the number of each atom.

Step-by-Step Guidance

Identify the formula: .
Count the number of Al atoms: 2.
Count the number of S atoms: 3 (from SO4, and there are 3 SO4 groups).
Count the number of O atoms: 4 per SO4 group, times 3 groups.

Try solving on your own before revealing the answer!

Q5. Choose from the following statements which are inconsistent with the implications and postulates of Dalton's atomic theory.

Background

Topic: Atomic Theory

This question tests your understanding of Dalton's atomic theory and its limitations.

Key concepts:

Atoms are indivisible and indestructible.
Atoms of the same element are identical.
Atoms combine in simple whole-number ratios.
Atoms cannot be created or destroyed.

Step-by-Step Guidance

Read each statement and compare it to Dalton's postulates.
Identify statements that contradict Dalton's theory (e.g., atoms being created, atoms having different masses).
List the inconsistent statements, but do not select the final answer yet.

Try solving on your own before revealing the answer!

Q6. Find the sulfur to fluorine ratio by mass in SF2 given that NS2 has a 2.29 ratio of sulfur to nitrogen and NF3 has a 4.07 ratio of fluorine to nitrogen.

Background

Topic: Law of Multiple Proportions

This question tests your ability to use mass ratios to compare elements in compounds.

Key concept:

Use the given ratios and atomic masses to set up a proportion for SF2.

Step-by-Step Guidance

Write the formula for SF2 and identify the number of S and F atoms.
Use atomic masses to calculate the mass of S and F in SF2.
Set up the ratio: .
Do not calculate the final ratio yet.

Try solving on your own before revealing the answer!

Q7. Calculate the charge-to-mass ratio in C/kg of an alpha particle, 4He2+, that has a mass of 4.00151 amu.

Background

Topic: Millikan Oil Drop Experiment / Charge-to-Mass Ratio

This question tests your ability to calculate the charge-to-mass ratio for a particle.

Key formulas:

1 amu = kg
Charge of =
Elementary charge = C

Step-by-Step Guidance

Convert the mass from amu to kg using kg.
Calculate the charge of the alpha particle: C.
Set up the charge-to-mass ratio formula.
Plug in the values, but do not calculate the final result yet.

Try solving on your own before revealing the answer!

Q8. Phosphorous-32 is a radioactive isotope of phosphorous and undergoes a beta decay to yield sulfur-32. If the two isotopes are to be differentiated using a mass spectrometer, what should be the precision of the mass spectrometer that is able to differentiate between the two?

Background

Topic: Rutherford Gold Foil Experiment / Mass Spectrometry

This question tests your understanding of isotope differentiation and mass spectrometer precision.

Key concept:

Precision must be at least as small as the mass difference between the two isotopes.

Step-by-Step Guidance

Find the mass difference between phosphorous-32 and sulfur-32.
Express the mass difference in grams.
Compare the mass difference to the options given for precision.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q9. Select the correct empirical formula for a substance with 11.34 mol C, 11.34 mol H, and 5.67 mol O.

Background

Topic: Empirical Formula

This question tests your ability to determine the simplest whole-number ratio of atoms in a compound.

Key formula:

Divide each mole value by the smallest number of moles to get the ratio.

Step-by-Step Guidance

Identify the mole values for C, H, and O.
Divide each by the smallest value (5.67).
Write the empirical formula based on the resulting ratios.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q10. The empirical formula of a compound is C10H13NO. Provide the molecular formula for C10H13NO if its molar mass is 326.432 g/mol.

Background

Topic: Molecular Formula

This question tests your ability to determine the molecular formula from the empirical formula and molar mass.

Key formula:

Step-by-Step Guidance

Calculate the mass of the empirical formula (add atomic masses for C, H, N, O).
Divide the given molar mass by the empirical formula mass to find n.
Multiply the subscripts in the empirical formula by n to get the molecular formula.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q11. An unknown compound consists of C, H, and N. When 0.227 g of the compound is ignited, it gives off 0.6581 g of CO2 and 0.1122 g of H2O. Determine its empirical formula and molecular formula if its molar mass is 273.33 g/mol.

Background

Topic: Combustion Analysis

This question tests your ability to determine empirical and molecular formulas from combustion data.

Key formulas:

Find moles of C from CO2:
Find moles of H from H2O:
Find moles of N by difference:
Convert masses to moles, then find the simplest ratio.

Step-by-Step Guidance

Calculate moles of C from CO2 produced.
Calculate moles of H from H2O produced.
Calculate mass and moles of N by difference.
Find the simplest ratio for empirical formula, then use molar mass to find molecular formula.

Try solving on your own before revealing the answer!

Q12. Give the name of the following ion formed by tellurium: TeO32–.

Background

Topic: Polyatomic Ions

This question tests your knowledge of naming polyatomic ions, especially those analogous to sulfur compounds.

Key concept:

Compare to the naming of SO32– (sulfite ion).

Step-by-Step Guidance

Identify the analogous sulfur ion (SO32–).
Apply the same naming convention to tellurium.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q13. Identify the names of the positive ions involved in each of the following compounds: A) MgO, B) K2SO4, C) NaBrO4, D) Co(NO3)2, E) Mn(OH)2.

Background

Topic: Naming Ionic Compounds

This question tests your ability to name cations in ionic compounds.

Key concept:

Identify the cation in each compound and use proper naming conventions (including Roman numerals for transition metals).

Step-by-Step Guidance

For each compound, identify the cation (positive ion).
Determine the charge and name of each cation.
Match the cation names to the answer choices, but do not select the final answer yet.

Try solving on your own before revealing the answer!

Q14. Provide the name and formula of the compound formed by magnesium and iodine.

Background

Topic: Writing Ionic Compounds

This question tests your ability to write formulas and names for binary ionic compounds.

Key concept:

Magnesium forms a ion, iodine forms a ion.
Balance charges to write the formula.

Step-by-Step Guidance

Write the ions: and .
Balance the charges to determine the formula.
Name the compound using standard conventions.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q15. Identify the formula of gallium nitrate pentahydrate.

Background

Topic: Naming Ionic Hydrates

This question tests your ability to write formulas for hydrated ionic compounds.

Key concept:

Gallium nitrate formula, plus 5 water molecules ().

Step-by-Step Guidance

Write the formula for gallium nitrate.
Add the hydrate part: .
Check answer choices for correct formula.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q16. Identify which pairing is incorrect: a. HBr, hydrobromide acid b. H2CrO4, chromic acid c. H2PO3, phosphoric acid d. HCl, hydrochloric acid

Background

Topic: Naming Acids

This question tests your knowledge of acid naming conventions.

Key concept:

Binary acids: "hydro-" prefix.
Oxoacids: based on polyatomic ion name.

Step-by-Step Guidance

Review each acid and its correct name.
Identify which pairings do not follow standard naming rules.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q17. Label the types of molecules: a) Chlorine b) C12H22O6 c) Copper d) Oxygen e) NH4Cl f) Argon

Background

Topic: Naming Molecular Compounds

This question tests your ability to classify substances as elements, compounds, and their types.

Key concept:

Monoatomic, diatomic, polyatomic elements, molecular and ionic compounds.

Step-by-Step Guidance

Identify each substance and classify it (element, compound, monoatomic, diatomic, etc.).
Match classifications to answer choices.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q18. Balance the following chemical equation: Co(NO3)3(aq) + (NH4)2CO3(aq) → Co2(CO3)3(s) + NH4NO3(aq)

Background

Topic: Balancing Chemical Equations

This question tests your ability to balance a chemical equation by adjusting coefficients.

Key concept:

Conservation of atoms: same number of each atom on both sides.

Step-by-Step Guidance

Write out the number of each atom on both sides of the equation.
Adjust coefficients to balance the atoms.
Check answer choices for the balanced equation.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q19. Rubidium metal reacts with iodine gas: 2Rb(s) + I2(g) → 2RbI(s). Initially, the reaction mixture contains 45.2 g Rb and 92.3 g I2. How many grams of the excess reactant remain after the reaction has occurred completely?

Background

Topic: Limiting Reagent

This question tests your ability to identify the limiting reagent and calculate the leftover excess reactant.

Key formulas:

Use stoichiometry to determine which reactant is limiting.
Calculate leftover excess reactant.

Step-by-Step Guidance

Calculate moles of Rb and I2 using their molar masses.
Use the reaction stoichiometry to determine the limiting reagent.
Calculate how much of the excess reactant is used.
Subtract used amount from initial to find remaining grams.

Try solving on your own before revealing the answer!

Q20. C2H5Cl is produced by the reaction of chlorine (Cl2) and ethane (C2H6). A) Calculate the theoretical yield of C2H5Cl when 172.8 g of C2H6 is reacted with 402.6 g of Cl2. B) If the reaction produces 153 g of C2H5Cl, calculate the percent yield.

Background

Topic: Percent Yield

This question tests your ability to calculate theoretical and percent yield in a chemical reaction.

Key formulas:

Use stoichiometry to find theoretical yield.

Step-by-Step Guidance

Calculate moles of C2H6 and Cl2.
Determine the limiting reagent.
Use stoichiometry to calculate theoretical yield of C2H5Cl.
Calculate percent yield using actual and theoretical yields.

Try solving on your own before revealing the answer!

Q21. Identify the element X in XBr4 given that it is 96.4 % Br by mass.

Background

Topic: Mass Percent

This question tests your ability to use mass percent to identify an unknown element in a compound.

Key formula:

Step-by-Step Guidance

Set up the equation for mass percent Br.
Plug in the atomic mass of Br and solve for the atomic mass of X.
Compare the calculated atomic mass to possible elements.
Do not select the final answer yet.

Try solving on your own before revealing the answer!

Q22. Is H3CCHCHCH2CH3 an alkane, alkene, or alkyne?

Background

Topic: Functional Groups in Chemistry

This question tests your ability to identify the type of hydrocarbon based on its structure.

Key concept:

Alkanes: only single bonds.
Alkenes: at least one double bond.
Alkynes: at least one triple bond.

Step-by-Step Guidance

Analyze the structure for double or triple bonds.
Determine which category the compound fits.
Do not select the final answer yet.