Refer to the two diagrams below to answer Questions 5 - 9
2H/10) 2010)
Reactants
2H O() 2H OM
286 kJ/mol
2H/a)
Products
288 kJ/mol
H,
Products Reactants
Combustion of hydrogen
Decomposition of water
5. How does this energy diagram differ from those in Lesson 11?
6. Consider the combustion of hydrogen.
a. Isenergy required to make the combustion of hydrogen happen? Use evidence from
the demonstration to explain your thinking,
b. Do you think the reaction feels hot or cold? Explain.

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)