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Chemical Reactions

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

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