Consider a solution consisting of the following two buffer systems:

H2CO3 HCO3– + H+ pKa = 6.4

H2PO4– HPO42– + H+ pKa = 7.2
At pH 6.4, which one of the following is true of the relative amounts of acid and conjugate base present?
***Please explain why the right answer is right and why the other ones are wrong.

a. [H2CO3] > [HCO3- ] and [H2PO4- ] > [HPO42- ]

b. [HCO3- ] > [H2CO3] and [HPO42- ] > [H2PO4- ]

c. [H2CO3 ] > [HCO3- ] and [HPO42- ] > [H2PO4- ]

d. [H2CO3] = [HCO3-] and [HPO42-] > [H2PO4- ]

e. [H2CO3] = [HCO3-] and [H2PO4- ] > [HPO42-]

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

Juju.01) 5 geologic events a group of students designed an experiment in an ice rink to represent the solar system. the steps of the experiment are listed below. 5: geologic events 1. choose a student to represent the sun. the planets are represented by two tennis balls. 2. ask the student to hold the tennis balls in each palm and spin on the ice with arms stretched out. 3. ask the student to draw in the arms after about 10 spins. 4. observe the student's arms rotate faster when they are closer to the body. 05 geologic events enors) the experiment most likely demonstrates that (2 points) 07 discussion-based sessment/module planets exert gravitational force on the sun the sun exerts gravitational force on the planets 3.07 discussion-based ssessment speed of a planet depends on its distance from the sun new version available! (3.0.119) get it now submit 18.07: module exam description

Describe at least two advantages and two disadvantages of using hydropower as a source of energy.