# Science

Balanced Equations:

you did not state what was added to the Zn so lets assume HCl.

Zn (s) +2 HCl (aq) -->  ZnCl2 (aq) + H2 (g)  Single replacement

In the second reaction the MnO2 acts as a catalyst in the decomposition of hydrogen peroxide.

2 H2O2 (aq) --> 2 H2O (aq) + O2 (g)

Reaction 3 is a synthesis reaction:

2 Cu (s) + O2 (g) --> 2 CuO (s)

Reaction 4 is a double replacement reaction.  The general form is:

AB (aq) + CD (aq) --> AC (aq)  + BD (s)

reaction 5 is a decomposition or dehydration type reaction:

CuSO4*5HOH (s) --> CuSO4 (s) + 5 HOH (l)

Reaction 6 is a synthesis or hydration reaction:

CuSO4 (s) + 5 HOH (l) -->  CuSO4*5HOH (s)

Reaction 7 is a single replacement reaction and is also an oxidation-reduction reaction>  The iron is oxidized and the copper is reduced.

Fe (s) + CuSO4 (aq)--> FeSO4 (aq)+ Cu (s)

Question 2:  the copper is combining with the oxygen in the air.

Question 3: the copper ion is being reduced to the element so the blue color gradually disappears.

Question 4:  common signs of a chemical reaction are:  release of heat or a gas; formation of a precipitate; change in color.