Question

balancing equations
name

1. a chemical reaction is a process in which

a. products change into reactants c. substances change state
b. the law of conservation of mass applies d. all of these

1. during a chemical reaction,

a. new elements are produced c. atoms are destroyed
b. atoms are rearranged d. elements are destroyed

1. an equation is balanced by

a. changing subscripts c. erasing elements as necessary
b. adding coefficients d. adding elements as necessary

1. an atom’s ability to undergo chemical reactions is determined by its

a. protons b. innermost electrons c. neutrons d. outermost electrons

1. what are the reactants in the following chemical equation:

zn + cuso₄ -----> znso₄ + cu
a. zinc and copper c. zinc and copper (ii) sulfate
b. zinc sulfate and copper d. only zinc

Explanation:

1. For a chemical reaction, the law of conservation of mass always applies; products form from reactants (not reverse), and state change is physical, so only b is correct.
2. Chemical reactions rearrange atoms; elements/atoms are not created or destroyed.
3. Balancing equations uses coefficients; subscripts cannot be changed as they define the compound.
4. An atom's reactivity depends on its outermost (valence) electrons, which participate in bonding.
5. Reactants are on the left side of a chemical equation arrow, so Zn (zinc) and CuSO₄ (copper (II) sulfate) are reactants.

Answer:

1. b. the law of conservation of mass applies
2. b. atoms are rearranged
3. b. adding coefficients
4. d. outermost electrons
5. c. zinc and copper (II) sulfate