The earth's atmosphere choose one: a. acquires its carbon dioxide from photosynthesis by green plants. b. became more oxygen-rich during the proterozoic, after the evolution of photosynthetic organisms in the archean. c. began as nitrogen and oxygen, left over from the solar nebula. d. gets warmer as its carbon dioxide concentration goes down.

Option (B)

Explanation:

The atmosphere refers to the gaseous envelope of the earth. It is comprised of various gases and is present at a definite proportion.

The amount of oxygen in the initial stage was significantly less. The ocean initially was comprised of a certain amount of oxygen, which was present in the dissolved state, and some of it was trapped in the iron-rich rocks commonly known as the Banded Iron Formation (BIF).

With the growing abundance of cyanobacteria, stromatolites, and other phytoplanktons and marine plants, the rate of photosynthesis eventually increased during the Precambrian period. Also, the land plants were developed during this time, and due to this increasing photosynthesis rate, the amount of oxygen in the earth's atmosphere gradually increased, thereby supporting a large number of living organisms.  

Thus, the earth became more oxygen-rich during the Proterozoic age (2500 to 540 million years back).

Hence, the correct answer is option (B).

answer: option (b) is the correct answer.

explanation:

a covalent bond is formed by sharing of electrons. whereas polarity arises due to difference in electronegativity of two atoms.

therefore, more is the electronegativity of an atom which combines with the titanium, more readily it will induce a partial positive and negative charge.

thus, out of the given options fluorine is most electronegative and has an incomplete octet. therefore, it will readily combine with titanium to share the electrons and complete its octet.  

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol