Chemical Reactions Quiz: MCQ Exam!

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Chemical Reactions Quiz: MCQ Exam! - Quiz


What do you know about chemical reactions? A chemical reaction is a route that leads to the transformation of one group of chemical substances to another. Chemical reactions exemplify changes that only involve electrons' positions in the developing and breaking of chemical bonds among atoms, with no change to the nuclei. This quiz will give you a positive reaction of happiness when you pass with flying colors.


Questions and Answers
  • 1. 

    Which one of the following represents a physical change?

    • A.

      Iron rusting

    • B.

      Paper burning

    • C.

      Water freezing

    • D.

      Dynamite exploding

    Correct Answer
    C. Water freezing
    Explanation
    Water freezing is a physical change because it involves a change in the state of matter from a liquid to a solid. The molecules in water slow down and come closer together as the temperature decreases, forming a solid ice. The chemical composition of water remains the same during this process, making it a physical change rather than a chemical reaction.

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  • 2. 

    .O {font-size:149%;} You can tell a chemical reaction because it always produces …

    • A.

      A different substance

    • B.

      Reactants

    • C.

      A change of state

    • D.

      Water

    Correct Answer
    A. A different substance
    Explanation
    A chemical reaction can be identified by the production of a different substance. This means that the reactants, which are the substances undergoing the reaction, combine and rearrange their atoms to form new substances with different chemical properties. This change in composition is a key characteristic of chemical reactions and distinguishes them from physical changes, such as changes in state or the formation of water.

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  • 3. 

    Slide 5 To balance a chemical equation, you should change only the…

    • A.

      Subscripts

    • B.

      Coefficients

    • C.

      Chemical formulas

    • D.

      Location of the arrow

    Correct Answer
    B. Coefficients
    Explanation
    To balance a chemical equation, you should change only the coefficients. Coefficients are the numbers that are placed in front of the chemical formulas to balance the number of atoms on both sides of the equation. By adjusting the coefficients, you can ensure that the same number of atoms of each element is present on both sides of the equation, maintaining the law of conservation of mass. Changing the subscripts would alter the chemical formula, which would represent a different compound altogether. The location of the arrow represents the direction of the reaction and does not affect the balancing of the equation.

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  • 4. 

    Slide 6 .O {font-size:149%;} If iron combines with oxygen to make iron oxide, the reactants are…

    • A.

      Iron oxide

    • B.

      Iron and iron oxide

    • C.

      Iron and oxygen

    • D.

      Oxygen and iron oxide

    Correct Answer
    C. Iron and oxygen
    Explanation
    When iron combines with oxygen to form iron oxide, the reactants involved in the chemical reaction are iron and oxygen. Iron reacts with oxygen to produce iron oxide.

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  • 5. 

    Slide 7 How many carbon atoms are there in  C12H22O11?

    • A.

      6

    • B.

      12

    • C.

      18

    • D.

      45

    Correct Answer
    B. 12
    Explanation
    The formula C12H22O11 represents a molecule of sucrose, which is a disaccharide made up of 12 carbon atoms. Therefore, the correct answer is 12.

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  • 6. 

    Slide 8 How many oxygen atoms are in the product of this equation: 2H2 + O2 --> 2H2O

    • A.

      2

    • B.

      4

    • C.

      8

    • D.

      12

    Correct Answer
    A. 2
    Explanation
    In the given equation, 2H2 + O2 -> 2H2O, the coefficient in front of O2 is 1. This means that there is only one molecule of O2 involved in the reaction. Since each molecule of O2 contains two oxygen atoms, the total number of oxygen atoms in the product (2H2O) is also 2.

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  • 7. 

    Slide 9 .O {font-size:149%;} Which one of the following is a chemical equation?

    • A.

      Ice + heat --> water

    • B.

      Iron + oxygen --> rust

    • C.

      CO2

    • D.

      C + O2 --> CO2

    Correct Answer
    D. C + O2 --> CO2
    Explanation
    The given answer, C + O2 --> CO2, is a chemical equation because it represents a chemical reaction between carbon (C) and oxygen (O2) to form carbon dioxide (CO2). In a chemical equation, the reactants are written on the left side of the arrow and the products are written on the right side. In this equation, C and O2 are the reactants, and CO2 is the product. The arrow indicates the direction of the reaction, showing the transformation of the reactants into the products.

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  • 8. 

    .O {font-size:149%;} Balance the following equation: Ag + O2 --> Ag2O

    • A.

      Put a 2 in front of Ag

    • B.

      Add a subscript 2 to the end of Ag2O

    • C.

      Add a 4 in front of Ag and a 2 in front of Ag2O

    • D.

      Add a 2 in front of Ag and a 1 in front of Ag2O

    Correct Answer
    C. Add a 4 in front of Ag and a 2 in front of Ag2O
    Explanation
    To balance the equation Ag + O2 --> Ag2O, you need to ensure that the number of each type of atom is the same on both sides of the equation. By adding a 4 in front of Ag and a 2 in front of Ag2O, you have balanced the equation. This is because now there are 4 atoms of Ag on both sides and 2 atoms of O on both sides, resulting in a balanced equation.

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  • 9. 

    .O {font-size:149%;} In a chemical equation, the arrow means what?

    • A.

      A reaction is happening.

    • B.

      The two sides are equal.

    • C.

      The products flow into reactants.

    • D.

      The equation is balanced.

    Correct Answer
    A. A reaction is happening.
    Explanation
    The arrow in a chemical equation indicates that a reaction is happening. It shows the direction in which the reactants are transforming into products. The arrow points from the reactants to the products, indicating the flow of the reaction.

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  • 10. 

    .O {font-size:149%;} The reactants include 7 grams of C and 4 grams of O. What is the total amount of C and O in the products?

    • A.

      7 grams

    • B.

      4 grams

    • C.

      11 grams

    • D.

      None

    Correct Answer
    C. 11 grams
    Explanation
    The total amount of C and O in the products is 11 grams because the question states that the reactants include 7 grams of C and 4 grams of O. When these reactants undergo a chemical reaction, they will combine to form products. Since the reactants are completely consumed in the reaction, the total amount of C and O in the products will be equal to the sum of the amounts in the reactants, which is 7 grams + 4 grams = 11 grams. Therefore, the correct answer is 11 grams.

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  • 11. 

    .O {font-size:149%;} Who first determined that the masses of the reactants and products must be the same?

    • A.

      Pasteur

    • B.

      Archimedes

    • C.

      Galileo

    • D.

      Lavoisier

    Correct Answer
    D. Lavoisier
    Explanation
    Lavoisier was the first to determine that the masses of the reactants and products must be the same. He conducted experiments on chemical reactions and observed that no mass was gained or lost during the process. This led him to propose the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Lavoisier's work laid the foundation for modern chemistry and our understanding of the conservation of mass in chemical reactions.

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  • 12. 

    .O {font-size:149%;} If you try to balance an equation by changing subscripts you change…

    • A.

      The number of molecules of product

    • B.

      The identity of the compound

    • C.

      The atomic number

    • D.

      The mass of the reactants

    Correct Answer
    B. The identity of the compound
    Explanation
    When balancing an equation by changing subscripts, you are altering the chemical formula of the compound. This means that you are changing the arrangement and type of atoms in the compound, thus changing its identity. The number of molecules of the product, the atomic number, and the mass of the reactants may be affected by balancing the equation, but the primary change is the identity of the compound itself.

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  • Current Version
  • Mar 22, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Mar 12, 2009
    Quiz Created by
    Wilstar
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