Wright Unit 5 Chemistry Test

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Wright Unit 5 Chemistry Test - Quiz

Questions and Answers
  • 1. 

    What is the molar mass of water?

    • A.

      18

    • B.

      18.02

    • C.

      17.01

    • D.

      16

    Correct Answer
    B. 18.02
    Explanation
    The molar mass of water is 18.02. This is because water is composed of two hydrogen atoms, each with a molar mass of 1, and one oxygen atom with a molar mass of 16. Adding these together gives a total molar mass of 18.02.

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  • 2. 

    What is the value used for Avogadro’s number?

    • A.

      6.0

    • B.

      6.02

    • C.

      6.02 x10^23

    • D.

      6.02 x 10^32

    Correct Answer
    C. 6.02 x10^23
    Explanation
    Avogadro's number is a fundamental constant in chemistry that represents the number of atoms or molecules in one mole of a substance. The value used for Avogadro's number is 6.02 x 10^23, which means that there are 6.02 x 10^23 atoms or molecules in one mole of a substance. This value is widely used in calculations involving the mole concept and is essential for understanding the relationships between mass, moles, and number of particles in chemistry.

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  • 3. 

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

    • A.

      Nitrogen dioxide

    • B.

      Aluminum phosphate

    • C.

      Sodium hydroxide

    • D.

      Lithium nitrate

    Correct Answer
    C. 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 charge of +1, and the hydroxide ion has a charge of -1. Therefore, to balance the charges, only one sodium atom is needed.

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  • 4. 

    A compound  is found to contain 46.66% nitrogen and 53.34 % oxygen, what is the empirical formula?

    Correct Answer
    B.
    Explanation
    The empirical formula of the compound can be determined by finding the ratio of the number of atoms of each element present in the compound. In this case, the compound contains 46.66% nitrogen and 53.34% oxygen. To find the ratio, we can assume a 100g sample of the compound. This means there would be 46.66g of nitrogen and 53.34g of oxygen. The molar mass of nitrogen is 14g/mol and the molar mass of oxygen is 16g/mol. Dividing the mass of each element by its molar mass gives us the number of moles. The ratio of moles of nitrogen to oxygen is approximately 3:2. Therefore, the empirical formula of the compound is N3O2.

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  • 5. 

    The molar mass for copper(II) sulfate pentahydrate is

    • A.

      159.6 g/mol

    • B.

      149.6 g/mol

    • C.

      259.6 g/mol

    • D.

      249.6 g/mol

    Correct Answer
    D. 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 all the elements 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. Since there are five water molecules (with two hydrogen atoms and one oxygen atom each) in the compound, we need to add the molar mass of water (18.0 g/mol) five times. Adding all these masses together gives a molar mass of 249.6 g/mol.

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  • 6. 

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

    Correct Answer
    C.
    Explanation
    The empirical formula gives the simplest whole number ratio of the atoms in a compound. In this case, the empirical formula is not given, so we cannot determine the molecular formula directly. However, since the molar mass is provided, we can calculate the empirical formula mass by summing the atomic masses of the elements in the empirical formula. Then, we can divide the molar mass by the empirical formula mass to find the number of empirical formula units in one molecule. This number will give us the ratio between the empirical formula and the molecular formula.

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  • 7. 

    Calculate the number of moles in 8.0 g of sodium hydroxide, NaOH.

    • A.

      .05

    • B.

      .10

    • C.

      .15

    • D.

      .20

    Correct Answer
    D. .20
    Explanation
    The correct answer is .20. To calculate the number of moles in a substance, you need to divide the given mass by the molar mass of the substance. The molar mass of sodium hydroxide (NaOH) is 40 g/mol. Therefore, dividing 8.0 g by 40 g/mol gives us 0.20 moles.

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  • 8. 

    In the following formula what is the substance that is reduced? 

    • A.

      Al

    • B.
    • C.
    • D.

      Cu

    Correct Answer
    D. Cu
    Explanation
    In the given formula, Cu is the substance that is reduced. Reduction is the process of gaining electrons, and in this case, Cu is undergoing reduction.

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  • 9. 

    In the following formula what is the substance that is oxidized? 

    • A.

      Al

    • B.
    • C.
    • D.

      Cu

    Correct Answer
    C.
    Explanation
    In the given formula, the substance that is oxidized is Al (aluminum).

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  • 10. 

    In the following formula what is the substance that is reducing agent? 

    • A.

      Al

    • B.
    • C.
    • D.

      Cu

    Correct Answer
    A. Al
    Explanation
    Aluminum (Al) is the substance that acts as the reducing agent in the given formula. A reducing agent is a substance that donates electrons to another substance, causing it to be reduced. In this case, Al is donating electrons to another substance, which indicates that it is undergoing oxidation itself. Therefore, Al is the reducing agent in the equation.

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  • 11. 

    In the following formula what is the substance that is oxidizing agent? 

    • A.

      Al

    • B.
    • C.
    • D.

      Cu

    Correct Answer
    B.
    Explanation
    The substance that is the oxidizing agent in the given formula is Cu.

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  • 12. 

    What type of reaction is this?

    • A.

      Synthesis

    • B.

      Decomposition

    • C.

      Single replacement

    • D.

      Double replacement

    Correct Answer
    C. Single replacement
    Explanation
    This reaction is a single replacement reaction, where one element replaces another element in a compound. In a single replacement reaction, a more reactive element replaces a less reactive element in a compound, resulting in the formation of a new compound.

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  • 13. 

    What are the correct coefficients for the following equation?

    • A.

      2, 4, 4, 2

    • B.

      1, 2, 3, 1

    • C.

      1, 2, 2, 1

    Correct Answer
    C. 1, 2, 2, 1
    Explanation
    The correct coefficients for the equation are 1, 2, 2, 1. This can be determined by comparing the given coefficients with the equation and finding the set of coefficients that correctly balances the equation.

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  • 14. 

     When the above equation is balanced, what is the coefficient for nickle (III) oxide?  

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    Correct Answer
    A. 1
    Explanation
    The coefficient for nickel (III) oxide is 1 because in a balanced equation, the coefficients represent the relative number of moles of each substance involved in the reaction. Since there is only one molecule of nickel (III) oxide in the equation, the coefficient for it is 1.

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  • 15. 

    What kind of reaction does the above equation represent?

    • A.

      Synthesis

    • B.

      Decomposition

    • C.

      Single replacement

    • D.

      Double replacement

    Correct Answer
    D. Double replacement
    Explanation
    The given equation represents a double replacement reaction. In a double replacement reaction, the positive and negative ions of two different compounds switch places, forming two new compounds. This is evident in the equation where the cations and anions of the reactants switch to form new compounds in the product.

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  • 16. 

    What are the reactants in the following equation? H2 + O2 → 2H2

    • A.

      Hydrogen

    • B.

      Oxygen

    • C.

      Water

    • D.

      Hydrogen and Oxygen

    Correct Answer
    D. Hydrogen and Oxygen
    Explanation
    The reactants in the given equation are hydrogen and oxygen. This is indicated by the chemical formula H2 for hydrogen and O2 for oxygen. The arrow in the equation represents the reaction, and the products are shown on the right side of the arrow, which in this case is 2H2O (water). Therefore, hydrogen and oxygen are the substances that undergo a chemical reaction to form water.

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  • 17. 

    Which is the balanced equation for zinc added to sulfuric acid producing hydrogen gas and zinc sulfate?

    Correct Answer
    D.
  • 18. 

    What is the percent of oxygen in Fe2(SO4)3?

    • A.

      48%

    • B.

      31%

    • C.

      35%

    • D.

      100%

    Correct Answer
    A. 48%
    Explanation
    The percent of oxygen in Fe2(SO4)3 can be determined by calculating the molar mass of oxygen in the compound and dividing it by the molar mass of the entire compound. Fe2(SO4)3 has a molar mass of 399.88 g/mol, and the molar mass of oxygen is 16.00 g/mol. The molar mass of oxygen in the compound is 3 * 16.00 g/mol = 48.00 g/mol. Therefore, the percent of oxygen in Fe2(SO4)3 is (48.00 g/mol / 399.88 g/mol) * 100% = 12.00%.

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  • 19. 

    How many moles are 345 g of Na?

    • A.

      5.73 mol

    • B.

      15.0 mol

    • C.

      7930 mol

    • D.

      9.03 mol

    Correct Answer
    B. 15.0 mol
    Explanation
    The molar mass of sodium (Na) is 22.99 g/mol. To find the number of moles, we divide the given mass (345 g) by the molar mass. Therefore, 345 g of Na is equal to 345/22.99 = 15.0 mol.

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  • 20. 

    Propane, C3H8 (g), burns in oxygen to form carbon dioxide and water.  Which equation correctly shows this reaction?    

    Correct Answer
    B.
    Explanation
    The correct equation for the combustion of propane is C3H8 + 5O2 → 3CO2 + 4H2O. This equation shows that one molecule of propane reacts with five molecules of oxygen to produce three molecules of carbon dioxide and four molecules of water.

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  • 21. 

    In which situation is a chemical reaction occurring?

    • A.

      Salt dissolving in water

    • B.

      A nail rusting

    • C.

      Ice melting

    • D.

      A glass window breaking

    Correct Answer
    B. A nail rusting
    Explanation
    A chemical reaction is occurring when a nail rusts. Rusting is a chemical process that involves the oxidation of iron in the presence of oxygen and water. This reaction results in the formation of iron oxide, or rust, which is a different substance than the original iron. In contrast, the other options mentioned - salt dissolving in water, ice melting, and a glass window breaking - are examples of physical changes rather than chemical reactions.

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  • 22. 

    Fossil fuels that contain carbon, such as coal, petroleum and natural gas, combine with oxygen to produce carbon dioxide gas and energy often in the form of heat.  These processes are example of which type of reactions?

    • A.

      Endothermic reactions

    • B.

      Metabolic reactions

    • C.

      Replacement reactions

    • D.

      Exothermic reaction

    Correct Answer
    D. Exothermic reaction
    Explanation
    Fossil fuels, such as coal, petroleum, and natural gas, undergo a chemical reaction with oxygen where they combine to produce carbon dioxide gas and energy in the form of heat. This release of energy in the form of heat indicates that the reaction is exothermic.

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