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Chemical Reactions

Practice Test
  1.As a result of the experiments of Lavoisier, you know that in a chemical reaction the mass of the products __________.  
  a.   is less than the mass of the reactants  
  b.   always equals the mass of the reactants  
  c.   is twice as great as the mass of the reactants  
  d.   cannot be predicted based on the mass of the reactants  
  2.The chemical formula for a compound tells __________ .  
  a.   how stable the compound is  
  b.   how electrons are arranged  
  c.   what type of chemical bond it forms  
  d.   what elements it contains  
  3.What does it mean for a chemical equation to be balanced?  
  a.   The number of reactants is equal to the number of products.  
  b.   The solid products weigh the same as the reactants.  
  c.   The same number of atoms of each element is on both sides of the equation.  
  d.   The reactants and the products are written with the same coefficients.  
  4.Some elements usually exist in combinations of two atoms. These combinations are called __________ .  
  a.   diatomic molecules  
  b.   coefficients  
  c.   isotopes  
  d.   ions  
  5.__________ is a way to describe a chemical reaction using chemical formulas and symbols.  
  a.   A chemical equation  
  b.   The law of conservation of matter  
  c.   Synthesis  
  d.   A physical law  
  6.A change in which one or more substances are converted into new substances is a __________ .  
  a.   chemical reaction  
  b.   physical change  
  c.   chemical fusion  
  d.   nuclear reaction  
  7.Why is oxygen written with a subscript 2?  
  a.   Its mass increases by two times as a result of the reaction.  
  b.   It usually exists as a diatomic molecule.  
  c.   Its mass is twice as great as the reactants'.  
  d.   There are two times as many oxygen atoms as reactant atoms.  
  8.In chemical equations, __________ represent the number of units of each substance.  
  a.   coefficients  
  b.   precipitates  
  c.   reactants  
  d.   products  
  9.In a __________ reaction, two or more substances combine to form another substance.  
  a.   synthesis  
  b.   decomposition  
  c.   single displacement  
  d.   double displacement  
  10.Which of the following is a chemical reaction?  
  a.   rust forming on a car body  
  b.   dew forming on grass  
  c.   water evaporating from salt water leaving salt crystals  
  d.   water freezing into ice  
  11.An insoluble compound that comes out of solution during a double displacement reaction is called a __________ .  
  a.   precipitate  
  b.   reactant  
  c.   catalyst  
  d.   solvent  
  12.New substances produced by a chemical reaction are __________ .  
  a.   reactants  
  b.   products  
  c.   coefficients  
  d.   resultants  
  13.A(n) __________ is a substance that speeds up a chemical reaction without being permanently changed itself.  
  a.   exotherm  
  b.   inhibitor  
  c.   endotherm  
  d.   catalyst  
  14.If electric current passes through water and initiates a decomposition reaction, what are the expected products?  
  a.   hydrogen peroxide  
  b.   hydrogen and oxygen  
  c.   hydrogen oxide  
  d.   oxygen and water  
  15.Ten grams of mercury(II) oxide react to produce 9.3 g of mercury and oxygen. What is the mass of the oxygen produced?  
  a.   7.0 g  
  b.   0.7 g  
  c.   1.7 g  
  d.   19.3 g  
  16.What type of reaction produces a precipitate?  
  a.   synthesis  
  b.   decomposition  
  c.   double displacement  
  d.   single displacement  
  17.The law of conservation of mass states that __________ .  
  a.   in a chemical reaction, matter is not created or destroyed, but is conserved  
  b.   in a chemical reaction, efforts should be made to preserve rare elements without changing them  
  c.   matter can be created and destroyed but does not change forms  
  d.   in a chemical reaction, the final mass of the products is always greater than the starting mass of the reactants  
  18.When iron combines with oxygen and water in the air to form rust, what substance in the reaction is the product?  
  a.   iron  
  b.   rust  
  c.   oxygen  
  d.   water  

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