Chemical Formulas, Equations And The Mole

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| By John Thompson
John Thompson, High school chemistry teaching
John, a dedicated educator, serves as the Chemistry teacher and Science Department Chair at New Castle High School in New Castle, IN. His commitment to science education and leadership in the department underscores his role in shaping the next generation of learners.
Quizzes Created: 3 | Total Attempts: 691
| Attempts: 300
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  • 1/10 Questions

    What is the correct formula for the compound formed when magnesium reacts with nitrogen?

    • MgN2
    • Mg3N2
    • Mg2N3
    • MgN
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Stoichiometry Quizzes & Trivia
About This Quiz

This AP Chemistry quiz focuses on chemical formulas, equations, and mole concepts. It assesses understanding of compound formation, molar mass calculations, and empirical formulas, enhancing skills crucial for academic success in advanced chemistry.

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  • 2. 

    A substance has an empirical formula of CH2O.  If the molar mass is 90 g/mol, what is the molecular formula?

    • CH2O

    • C2H4O2

    • C3H6O3

    • C4H8O4

    Correct Answer
    A. C3H6O3
    Explanation
    The empirical formula of CH2O tells us that there is one carbon atom, two hydrogen atoms, and one oxygen atom in the compound. The molar mass of 90 g/mol suggests that the compound has a molecular formula that is three times the empirical formula. Therefore, the molecular formula is C3H6O3, which means there are three carbon atoms, six hydrogen atoms, and three oxygen atoms in the compound.

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  • 3. 

    The molar mass for copper(II) sulfate pentahydrate is

    • 149.6 g/mol

    • 249.6 g/mol

    • 159.6 g/mol

    • 259.6 g/mol

    Correct Answer
    A. 249.6 g/mol
    Explanation
    The molar mass for copper(II) sulfate pentahydrate is 249.6 g/mol. This can be determined by adding up the atomic masses of each element in the compound. Copper has a molar mass of 63.5 g/mol, sulfur has a molar mass of 32.1 g/mol, oxygen has a molar mass of 16.0 g/mol, and hydrogen has a molar mass of 1.0 g/mol. Additionally, there are five water molecules (H2O) in the compound, which have a total molar mass of 90.0 g/mol (18.0 g/mol per water molecule). Adding all these masses together gives a molar mass of 249.6 g/mol for copper(II) sulfate pentahydrate.

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  • 4. 

    Which of the following compounds has a formula with no subscripts?

    • Nitrogen dioxide

    • Aluminum phosphate

    • Sodium hydroxide

    • Lithium nitrate

    Correct Answer
    A. Sodium hydroxide
    Explanation
    Sodium hydroxide has a formula with no subscripts because it consists of only one sodium atom and one hydroxide ion. The sodium ion has a +1 charge, while the hydroxide ion has a -1 charge. Therefore, to balance the charges, only one of each atom is needed, resulting in a formula of NaOH.

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  • 5. 

    A nitrogen oxide is found to contain 46.66% nitrogen, what is the empirical formula?

    • N2O3

    • NO

    • NO2

    • N2O

    Correct Answer
    A. NO
    Explanation
    The given compound is found to contain 46.66% nitrogen. The empirical formula of a compound represents the simplest whole number ratio of the elements present in it. Since nitrogen is the only element present in the compound, the empirical formula would be NO.

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  • 6. 

    What is the correct formula for sodium peroxide?

    • NaO

    • Na2O

    • Na2O2

    • NaO2

    Correct Answer
    A. Na2O2
    Explanation
    The correct formula for sodium peroxide is Na2O2. This is because sodium peroxide is a compound composed of two sodium atoms (Na2) and two oxygen atoms (O2). The subscript 2 indicates that there are two of each element in the compound.

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  • 7. 

    How many iron ions are in the formula for iron(III) phosphate?

    • 1

    • 2

    • 3

    • 4

    Correct Answer
    A. 1
    Explanation
    Iron(III) phosphate is represented by the formula FePO4. In this formula, there is only one iron ion (Fe3+) present. The Roman numeral III indicates that the iron ion has a charge of +3. Therefore, the correct answer is 1.

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  • 8. 

    For the reaction of sodium with hydrogen, what mass of sodium hydride is formed from the complete reaction of 2.00 g of hydrogen?

    • 12 g

    • 24 g

    • 96 g

    • 48 g

    Correct Answer
    A. 48 g
    Explanation
    The molar ratio between sodium and hydrogen in the reaction is 2:1. This means that for every 2 moles of sodium, 1 mole of hydrogen is required. Since we are given the mass of hydrogen (2.00 g), we need to convert it to moles using the molar mass of hydrogen (1 g/mol). 2.00 g of hydrogen is equal to 2.00 moles. Since the molar ratio is 2:1, we need half the moles of sodium as the moles of hydrogen. Therefore, 1.00 moles of sodium is required. The molar mass of sodium hydride is 48 g/mol, so 1.00 moles of sodium hydride would have a mass of 48 g.

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  • 9. 

    If 2.00 g of hydrogen gas is combined with 2.00 g of oxygen gas, what mass of water could be produced?

    • 2.25 g

    • 3.75 g

    • 18.0 g

    • 4.00 g

    Correct Answer
    A. 2.25 g
    Explanation
    When hydrogen gas (H2) and oxygen gas (O2) react to form water (H2O), the ratio of their masses is 2:16. This means that for every 2 grams of hydrogen gas, 16 grams of oxygen gas are needed to produce 18 grams of water. In this case, 2 grams of hydrogen gas and 2 grams of oxygen gas are combined, which is the exact amount needed to produce 18 grams of water. Therefore, the mass of water that could be produced is 18 grams.

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  • 10. 

    For the reaction: 3A + 5B -> 2C + D, where 6 mol A is combined with 2.5 mol B, what is the percent yield (by moles) if 0.3 mol D is actually made?

    • 30%

    • 40%

    • 50%

    • 60%

    Correct Answer
    A. 60%
    Explanation
    The percent yield is calculated by dividing the actual yield (0.3 mol D) by the theoretical yield and multiplying by 100. To find the theoretical yield, we need to determine the limiting reactant. Using the given amounts, we can calculate the moles of C and D that would be produced if all the A and B reacted completely. From the balanced equation, we can see that 3 moles of A react with 5 moles of B to produce 2 moles of C and 1 mole of D. Therefore, if 6 mol A reacts with 2.5 mol B, the theoretical yield of D would be (6 mol A / 3 mol A) * (1 mol D / 1 mol D) = 2 mol D. The percent yield is (0.3 mol D / 2 mol D) * 100 = 60%.

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  • Current Version
  • Mar 19, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Sep 24, 2009
    Quiz Created by
    John Thompson

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