chemistry study

Which observation does NOT indicate that a chemical reaction has occurred?

• formation of a precipitate

  
  

• evolution of heat

  
  

• production of gas

• change in total mass of substances

  
  

After the correct formula for a reactant in an equation has been written, the...

• subscripts are adjusted to balance the equation

  
  

• formula should not be changed

  
  

• same formula must appear as the product

  
  

• symbols in the formula must not appear on the product side of the equation

  
  

To balance a chemical equation, it may be necessary to adjust the

• coefficients

• formulas of the products

  
  

• subscripts

• number of product

  
  

According to the law of conservation of mass, the total mass of the reacting substances is

• always more than the total mass of the products

  
  

• always more than the total mass of the products

• sometimes more and sometimes less than the total mass of the products

  
  

• always equal to the total mass of the products

  
  

When the equation Fe3O4 +Al--> Al2O3 +Fe is correctly balanced, what is the coeifcient of Fe?

• 3

• 4

• 6

• 9

which coefficients correctly balance the formula equation NH4NO2-> N2+H2O?

• 1,2,2

• 1,1,2

• 2,1,1

• 2,2,2

which coefficients correctly balance the formula equation CaO+H2O --> Ca(OH)2?

• 2, 1, 2

  
  

• 1, 2, 3

  
  

• 1, 2, 1

  
  

• 1,1,1

Which equation is NOT balanced?

• 2H2 + O2 --> 2H2O

  
  

• H2 + H2 + O2 --> H2O + H2O

  
  

• 4H2 + 2O2 --> 4H2O

  
  

• fjkfjweh

the equation AX --> A + X is the general equation for a

• synthesis reaction

  
  

• combustion reaction

  
  

• decomposition reaction

  
  

• single-replacement reaction

  
  

A chemical bond results from the mutual attraction of the nuclei of atoms and

• neutrons

• electrons

  
  

• protons

• dipoles