Victor Grade 7 - Science - Chemical Reactions Practice Test

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Costi
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258119
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Victor Grade 7 - Science - Chemical Reactions Practice Test
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2014-01-25 15:11:37
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Chemical Reactions
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Chemical Reactions
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  1. Synthesis occurs when….
    simple molecules become complex.
  2. In decomposition...
    complex molecules become simple.
  3. What is found on the Left Side of an equation?
    Reactants are found on the Left Side of an equation.
  4. What is found on the right side of an equation?
    Products are found on the right side of an equation.
  5. What type of reaction absorbs energy?
    An endothermic reaction absorbs energy.
  6. What is a reaction with an element and a compound that forms a different compound and a different element?
    A single replacement reaction is a reaction with an element and a compound that formsdifferent compound and a different element.
  7. What is a reaction between 2 complex compounds that produce 2 different complex compounds?
    A double replacement is a reaction between 2 complex compounds that produce 2 different complex compounds.
  8. What is a reaction that releases energy?
    An exothermic reaction is a reaction that releases energy.
  9. What is the Law of Conservation and Mass?
    The Law of Conservation and Mass states that the number of atoms in the reactants must equal the number of atoms in the products.
  10. Electrons in the outermost energy level are called…….
    Valence Electrons.
  11. In the chemical formula for H2O, the number 2 is the ___________.
    Subscript.
  12. A substance that can speed up a reaction but is not charged or used up in the reaction is a...
    Catalyst.
  13. Which of the follow will DECREASE the rate at which a reaction will take place?

    A. heat
    B. lower the concentration
    C. add a catalyst
    D. greater surface area
    B. lower the concentration

    will DECREASE the rate at which a reaction will take place.
    (this multiple choice question has been scrambled)
  14. Any number written in front of a molecule is called a…

    A. coefficient
    B. superscript
    C. subscript
    D. formula number
    A. coefficient
    (this multiple choice question has been scrambled)
  15. What is it called when complex molecules become simple?
    Decompostion.
  16. In a typical relationship, temperature and rate of chemical reaction both…..
    INCREASE.
  17. What kind of reaction is this?

    2H2O  ____>  2H2 + O2
    a Decomposition reaction
  18. The reaction Mg ___> 2HCI ___> MgCl2 + H2

    would be considered what type of reaction?
    A Single Replacement reaction
  19. H2 + Cl2 ____> 2HCl

    illustrates what?
    The Conservation of Mass
  20. When an exothermic reaction occurs in a water solution, the temperature of the solution….
    Increases because energy is given off by the reaction.
  21. Cu(s) + 2HCl(aq) ___> H2(g) + CuCl2(aq)

    is an example of a ...
    Single Replacement reaction
  22. True or false...

    An endothermic reaction absorbs heat
    TRUE
  23. A neutral atom always has equal numbers of ?
    protons and neutrons.
  24. Charcoal reacts with oxygen according to the equation...

    C(s) + O2(g) ____> CO2(g)

    Which of the following changes would cause the greatest increase in the rate of reaction?

    a. cooling the O2 gas
    b. decreasing the concentration of O2
    c. using charcoal in powdered form
    d. using charcoal in lump form
    c. using charcoal in powdered form
  25. Atoms become positive ions by...
    losing electrons
  26. In which group does each element have a total of four electrons in the outermost principal energy level?

    a. 1 (IA)
    b. 18 (O)
    c. 16 (VIA)
    d. 14 (IVA)
    d. 14 (IVA)
  27. The addition of a catalyst to a chemical reaction would result in a change in the….
    activation energy.
  28. A chemical reaction is usually started by providing the necessary….
    activation energy.
  29. As a Na atom forms an Na ion, the number of protons in its nucleus….
    remains the same.
  30. What is the number of valence electrons in an atom of phosphorus?
    five
  31. Use the compound below and answer the questions that follow.

    2 NaOH

    # molecules ____
    # elements ____
    #Na _____
    # O _____
    #H ______
    • # molecules = 2
    • # elements = 3
    • # Na = 2
    • # O = 2
    • # H = 2
  32. List three things that are evidence of a chemical reaction….
    • 1. gas production
    • 2. color change
    • 3. property change
    • 4. temperature change
    • 5. precipitation
  33. In a synthesis reaction, two or more simple substances combine to form a new, more complex substance.  The generalized equation for a synthesis reaction is as follows….
    A + B __________> AB

    Where A and B represent elements from the periodic table.  

    • For example: Na + Cl _________> NaCl
  34. In a Decomposition Reaction, a complex substance breaks down into two or more simple substances.  Decomposition reactions are the reverse of synthesis reactions.  The generalized equation for a decomposition reaction is as follows….
    AB _________> A + B


    Where A and B represent elements from the periodic table.  

    For example:

    NaCl _________> Na + Cl2
  35. In a Single Replacement Reaction, an uncombined element replaces an element that is part of a compound.  The generalized equation for a single replacement reaction is as follows...
    A + BC _________>  AC + B

    In this reaction the A and B switched places, or replaced each other, in the reaction.  A, B, and C represent elements from the periodic table.  

    For example:

    Na + H2O  _________>  NaOH + H2

    • In this case, the sodium and the hydrogen switched places.
  36. In a Double Replacement Reaction, different atoms in two different compounds replace each other.  In other words, two compounds react to produce two new compounds.  The generalized equation for a double replacement reaction is as follows...
    AB + CD ________> AC + BD

    In this reaction, the elements from both compounds switched places, or replaced each other, in the compounds to form two new compounds.  A, B, C, and D represent elements on the periodic table.

    For example:

    NaOH + HCl  ________> NaCl + H2O

    in this case, the sodium and the hydrogen replaced each other and formed two new compounds from the original compounds.
  37. Label each of the following reactions as synthesis, decomposition, single replacement, and double replacement.
    KCl + Pb(NO3)2 ___> K(NO3) + PbCl2 = Double Replacement

    N2 + O2 ____> NO2 =  Synthesis

    C6H12O6 ____> CO2 + H2O = Decomposition

    Zn + HCl ____> ZnCl2 + H2 = Single Replacement

    MgO ____> Mg + O2  = Decomposition

    H2O + Fe ____> Fe2O3 + H2 = Single Replacement

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