The pH of a sample of lake water was originally 6 when measured in 1987. When measured again in 2014, the pH of the water was 4. How has the concentration of hydrogen ions in the lake changed?
a. The concentration of hydrogen ions has increased by a factor of 2.
b. The concentration of hydrogen ions has increased to 10 times its original value.
c. The concentration of hydrogen ions has increased to 100 times its original value.
d. The concentration of hydrogen ions has decreased by a factor of 2.

Perform the following mathematical operations and report the answer to the appropriate number of significant figures 5.87998 + 3.100

Different isotopes indicate that an element will have different numbers of

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.)