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Chemical Reactions

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

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