Scientists have hypothesized that oxygen began to build up in the earth's atmosphere after the development of living things with the ability to
a. breathe air.
b. form tissues.
c. photosynthesize.
d. reproduce sexually.

c. photosynthesize.

Explanation:

It is believed that it was life itself that originated all this oxygen present on the planet and promoted the change in the composition of the earth's atmosphere. This change would have begun, according to paleontologists, when the ability to perform photosynthesis emerged during the evolution of living beings. Commonly associated with plants, the ability to produce oxygen is also common to bacteria such as blue algae, unicellular beings that live in the oceans and, despite their name, are more similar to bacteria than algae. The great virtue of photosynthesis is to convert sunlight and carbon dioxide into energy for metabolism. As a byproduct, oxygen is released.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: