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Quizzes > High School Quizzes > Science

Chapter 7 Review: Chemical Formulas Practice Quiz

Master Unit 7 Names and Formulas Test Review

Difficulty: Moderate
Grade: Grade 10
Study OutcomesCheat Sheet
Colorful paper art promoting a high school math trivia quiz named Formula Frenzy.

What does a chemical formula represent?
The energy levels of electrons in an atom
The types and ratios of elements in a compound
The physical state of a compound at room temperature
The cost of elements in a market
A chemical formula provides information about which elements are present in a compound and in what proportions. This understanding is fundamental to analyzing chemical composition.
How many different types of atoms are present in H2O?
One
Four
Three
Two
H2O contains hydrogen and oxygen, meaning there are two distinct elements. Although the molecule has three atoms in total, the question focuses on the types of atoms.
Which formula correctly represents sodium chloride?
NaCl
Na2Cl2
NaCl2
Na2Cl
Sodium chloride is made of sodium and chlorine in a 1:1 ratio, which is correctly written as NaCl. This notation reflects the simplest combination needed for electrical neutrality.
In the compound CO2, how many oxygen atoms are present?
Two
Four
Three
One
CO2 contains one carbon atom and two oxygen atoms as indicated by the subscript 2. Recognizing subscripts is key to reading chemical formulas correctly.
What does a subscript in a chemical formula indicate?
The number of electrons lost
The compound's boiling point
The charge of an ion
The number of atoms of an element in a molecule
A subscript tells you how many atoms of a particular element are in one molecule of a compound. This is essential for determining the compound's actual composition.
What is the difference between an empirical formula and a molecular formula?
An empirical formula contains polyatomic ions, while a molecular formula does not.
They are two terms for the same representation.
An empirical formula includes subscripts, while a molecular formula does not.
An empirical formula shows the simplest ratio of elements, while a molecular formula gives the actual number of atoms.
The empirical formula represents the simplest whole-number ratio of the elements in a compound, whereas the molecular formula indicates the actual number of each type of atom present. This distinction is crucial when analyzing chemical compositions.
What is the correct formula for aluminum sulfate?
Al(SO4)2
AlSO4
Al2(SO4)3
Al2SO4
Aluminum sulfate contains two aluminum atoms and three sulfate groups, which is represented as Al2(SO4)3. This correct formulation ensures proper charge balance between the ions.
Which compound is represented by the formula CaCO3?
Calcium Carbonate
Calcium Oxide
Calcium Chloride
Calcium Hydroxide
CaCO3 stands for calcium carbonate, a common compound found in rocks and shells. Recognizing constituent ions, such as Ca2+ and CO3^2-, helps to decode the formula.
Identify the oxidation state of oxygen in most compounds.
+2
-1
-2
0
Oxygen typically has an oxidation state of -2 in compounds, except in peroxides and a few special cases. This rule aids in balancing chemical equations and understanding redox behavior.
What is the correct formula for magnesium oxide?
Mg2O3
MgO
MgO2
Mg2O
Magnesium oxide is composed of magnesium and oxygen in a 1:1 ratio, which is represented simply as MgO. The formula reflects the balanced charges of Mg2+ and O2-.
How are parentheses used in chemical formulas?
They indicate that a group of atoms acts as a single unit.
They indicate a reaction condition.
They show the molecular weight of the compound.
They separate cations from anions.
Parentheses are used to group atoms, especially in polyatomic ions, to show that they function as a single unit within a compound. This notation is essential for capturing the structure of complex compounds.
What process is used to calculate the molar mass of a compound?
Dividing the number of molecules by its atomic mass.
Subtracting the mass of electrons from the atomic mass.
Multiplying the number of atoms by the compound's volume.
Adding the atomic masses of all atoms in its chemical formula.
To calculate the molar mass, you sum the atomic masses of all the atoms present according to the compound's chemical formula. This calculation is a cornerstone of stoichiometry in chemistry.
What is the chemical formula for dinitrogen tetroxide?
N4O2
NO2
N2O4
N2O3
Dinitrogen tetroxide is composed of 2 nitrogen atoms and 4 oxygen atoms, leading to the formula N2O4. This naming follows the standard prefix rules used in chemistry.
How many total atoms are present in one molecule of glucose, C6H12O6?
12
18
24
36
In C6H12O6, you add 6 (carbon) + 12 (hydrogen) + 6 (oxygen) to get a total of 24 atoms. This question reinforces counting atoms in a molecular formula.
Which of the following statements about empirical formulas is true?
They always include the number of molecules present.
They represent the simplest whole-number ratio of the elements.
They show the actual numbers of atoms in a molecule.
They indicate the physical state of a compound.
An empirical formula expresses the simplest whole-number ratio of elements in a compound, not the precise count of atoms. This simplification is useful when the actual molecular structure is not required.
What is the percent composition of oxygen in carbon dioxide (CO2)?
Approximately 73%
Approximately 55%
Approximately 50%
Approximately 27%
The mass of oxygen in CO2 is 2 × 16 = 32 g, and the total molar mass is 12 + 32 = 44 g. Thus, the percent composition of oxygen is (32/44) × 100, which is approximately 73%.
A compound is composed of 40.0% sulfur and 60.0% oxygen by mass. What is its empirical formula?
SO2
S2O3
SO3
S2O5
Calculating moles: for sulfur, 40.0 g/32 g/mol ≈ 1.25 and for oxygen, 60.0 g/16 g/mol ≈ 3.75; the simplest whole-number ratio is 1:3, yielding the empirical formula SO3. This method is standard for determining empirical formulas from percentage composition.
The empirical formula of a compound is CH2 and its molar mass is 56 g/mol. What is its molecular formula?
C4H8
C5H10
C3H6
C2H4
The empirical formula CH2 has a molar mass of 14 g/mol. Dividing the given molar mass (56 g/mol) by 14 gives a factor of 4, resulting in the molecular formula C4H8. This illustrates how molecular formulas are derived from empirical formulas.
Which compound is represented by the formula NH4NO3?
Nitrous Oxide
Ammonium Nitrate
Nitrate Ammonium
Ammonia
NH4NO3 is composed of the ammonium ion (NH4+) and the nitrate ion (NO3-), which combine to form ammonium nitrate. This compound is familiar in both chemical applications and everyday contexts, such as fertilizers.
In the hydrated salt CuSO4·5H2O, how many total atoms are present in one formula unit?
20
24
18
21
CuSO4 contains 1 copper, 1 sulfur, and 4 oxygen atoms. The 5H2O adds 10 hydrogen and 5 oxygen atoms. Adding these gives 1+1+4+10+5 = 21 atoms in total. This problem reinforces counting atoms in complex, hydrated compounds.
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Study Outcomes

  1. Analyze chemical formulas to identify constituent elements and their proportions.
  2. Apply mathematical operations to solve for unknown values in chemical compounds.
  3. Synthesize formula-based calculations to determine molecular compositions.
  4. Evaluate relationships between chemical formulas and compound structures.

Chapter 7 Chemical Quiz Formulas & Comps Cheat Sheet

  1. Empirical vs Molecular Formulas - Two compounds with the same atoms can look very different! The empirical formula gives you the simplest whole‑number ratio of each atom, while the molecular formula spells out the exact count in a molecule. Mastering this difference helps you interpret chemical compositions like a pro. Wikipedia: Empirical formula
  2. Ionic Compound Naming - Naming ionic compounds is like pairing dance partners: the positively charged cation leads, followed by the negatively charged anion. Make sure you get the order right and balance the charges so your compound stays neutral. Nail this, and you'll breeze through salt names like NaCl or MgO! Brainscape: Ionic naming
  3. Covalent Prefixes - Prefixes like mono‑, di‑, and tri‑ tell you exactly how many atoms of each element are in a molecular compound. Forgetting them can turn carbon dioxide (CO₂) into carbon monoxide (CO)! Practice these prefixes until they roll off your tongue. Brainscape: Covalent prefixes
  4. Oxidation Numbers - Think of oxidation numbers as a bookkeeping system for electron ownership in bonds. Assigning these charges helps you predict redox reactions and track electron flow. It's like keeping score in an epic electron tug‑of‑war! Brainscape: Oxidation numbers
  5. Acid Nomenclature - Acids come in two flavors: binary acids (hydrogen + one nonmetal) and oxyacids (hydrogen + oxygen + another element). Naming them correctly involves special endings like ‑ic and ‑ous, so you'll know whether you're dealing with HCl or H₂SO₄. Acid naming never tasted so fun! Brainscape: Acid naming
  6. Formula Mass Calculation - To find a compound's formula mass, add up the atomic masses of all atoms in its formula. It's like tallying up your chemistry shopping list - every element counts! Precision here sets you up for success in stoichiometry and beyond. CourseSidekick: Formula mass guide
  7. Percentage Composition - Percentage composition tells you how much each element contributes by mass to a compound. It's a handy way to see which element really steals the show in your sample. Use it to check purity or predict yields in reactions! Brainscape: Percent composition
  8. Practice Writing Formulas - Flip between names and formulas until it feels like muscle memory - H₂O ↔ water, Na₂CO₃ ↔ sodium carbonate. Correct subscripts and element symbols are your best friends here. The more you practice, the fewer "oops" moments you'll have on exams. ChemistryProf: Formulas & nomenclature
  9. Polyatomic Ions - Polyatomic ions are groups of atoms that stick together with an overall charge - like the sulfate ion (SO₄²❻) or ammonium (NH₄❺). Recognizing these is crucial because they pop up everywhere in salts and acids. Learn their names and charges, and you'll decode complex formulas at lightning speed! ChemistryProf: Polyatomic ions
  10. Hydrates - Hydrates are compounds that carry extra water molecules in their crystal structure, shown by a dot like CuSO₄·5H₂O. Knowing how to name and calculate their mass helps you avoid surprises when crystals lose or gain water. It's chemistry with a splash! Brainscape: Hydrates
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