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Chemical Reactions

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

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