GED Practice

GED Science Review: Chemical Reactions

Questions:

Directions: Choose the answer to each question.

Question 1 refers to the passage below.

Atoms of most elements can bond with other atoms. When atoms bond they either transfer or share electrons. If electrons are transferred from one atom to another, each atom takes on a charge; charge atoms are called ions. A bond between ions is an ionic bond. Ionic bond form only between two different elements; the substance that result are ionic compounds. Elements on opposite sides of the periodic table are most likely to join by ionic bonding. Elements closer to each other in the periodic table tend to bond by sharing electrons. Bonds that result when electrons are shared are called covalent bonds. A single covalent bond requires a pair of electrons be shared; one electron comes from each atom. Two or more atoms joined by a covalent bond from a molecule.
Covalent bonds can form between atoms of the same element  or between atoms of two or more different elements. When atoms of different elements are joined by covalent bonds, the result is a covalent compound.

  1. Which situation involves ionic bonding?
    • oxygen and nitrogen gases mixed together in air
    • sugar molecules dissolved in water to form sugar water
    • two hydrogen atoms and an oxygen atom sharing two pairs of electrons
    • calcium giving up two electrons to fluorine atoms to form calcium fluoride

      Questions 2 and 3 refer to the following passage and diagram.

      Compounds can be represented by chemical formulas, structural formulas, and diagrams. For example, the compound methane is shown by the chemical formula CH4. The C stands for carbon, and H stands for hydrogen. The numbers tell you how many atoms are in one molecule of methane. When there is no number, that means there is one atom. Thus, a molecule of methane has one atom of carbon and four atoms of hydrogen.

  2. The structural formula for propane is shown here.



    Which statement is supported by the structural formula for propane?
    • Propane contains nitrogen atoms.
    • The chemical formula for propane is C3H6
    • The chemical formula for propane is C3H8
    • Propane contains more carbon atoms than hydrogen atoms.
  3. When propane burns in air, it reacts with oxygen (O) to form carbon dioxide (CO) and water (HO). Which balanced chemical equation describes this reaction?
    • C3H8 + O2 –> CO2 + H2O
    • C3H8 + 4O2 –> CO2 + 4H2O
    • C3H8 + 5O2 –> 3CO2 + H2O
    • C3H8 + 5O2 –> 3CO2 + 4H2O

      Questions 4 through 6 refer to the following passage and chart.

      Labels on food often list amounts of saturated and unsaturated fats. A saturated molecule is one that contains only single bonds, in which one pair of electrons is shared in each bond. Unsaturated molecules contain other types of bonds, in which more than one pair of electrons are shared.
      A saturated hydrocarbon is saturated with hydrogen. That is, it contains more hydrogen than an unsaturated hydrocarbon with the same number of carbon atoms. One example of a saturated hydrocarbon is ethane, C2H6. An example of an unsaturated molecule is ethane, C2H4. In the unsaturated hydrocarbon ethane, two electrons of one carbon atom are paired with two electrons of another carbon atom, forming a double bond.
      In certain reactions, the double and triple bonds of an unsaturated hydrocarbon can be broken. Hydrogen can then be added to the molecule. A reaction in which hydrogen is added to an unsaturated hydrocarbon is called an addition reaction.

  4. Which element is required for an addition reaction involving hydrocarbons?
    • hydrogen
    • lithium
    • nitrogen
    • oxygen
  5. In contrast to a saturated molecule, what does an unsaturated molecule contain?
    • carbon atoms
    • double bonds
    • hydrogen ions
    • shared electrons
  6. Which conclusion regarding addition reactions is supported by the information presented?
    • Both reactants are hydrocarbons.
    • One reactant is a saturated hydrocarbon.
    • The number of carbon atoms in the original molecule increases.
    • Saturated hydrocarbons are produced from unsaturated hydrocarbons.
  7. The law of conservation of mass states that matter is neither created nor destroyed in normal chemical reactions. In the chemical reaction below, the symbols A and B represent reactants and the symbols C and D represent products. The masses of A, B, and C are given. When the reaction goes to completion, how many grams of substance D will be produced?

    A + B –> C + D
    A = 4.6 g
    B = 7.3 g
    C =  9.2 g
    D = ________ g
  8. In photosynthesis, carbon dioxide and water are converted to glucose and oxygen. The net unbalanced equation for photosynthesis is given. Write the balanced equation.

    CO2 + H2O –> C6H12O6 + O2
    ______________________________________
Answer:

  1. calcium giving up two electrons to fluorine atoms to form calcium fluoride
  2. The chemical formula for propane is C3H8
  3. C3H8 + 5O2 –> 3CO2 + 4H2O
  4. hydrogen
  5. double bonds
  6. Saturated hydrocarbons are produced from unsaturated hydrocarbons.
  7. 2.7
  8. 6CO2 + 6H2O –> C6H12O6 + 602







Reference:


Complete Test Preparation for the GED Test 2014 by Steck-Vaughn