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.

According to each substances heat of fusion, which of the items below requires more heat to be added per gram of substance to go from solid to liquid? silver sulfur water lead

According to the valence shell electron pair repulsion (vsepr) theory, a molecule that has four electron groups around the central atom will exhibit what electron geometry? view available hint(s) according to the valence shell electron pair repulsion (vsepr) theory, a molecule that has four electron groups around the central atom will exhibit what electron geometry? trigonal bipyramidal tetrahedral square planar determination of electron geometry requires information on whether the electron groups are lone pairs or bonding groups.

Oil rich countries in the middle east cover about 4% of earths total land area but prossess about 48% of the worlds known oil reserves what is the main reason for high concentration of reserves in this part of the world