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denis-greek [22]
2 years ago
13

The fossil pictured above came from the St. Clair Site in Pennsylvania. The fossils are formed in black slate of the Pennsylvani

an Period, 300 million years ago. The fossils found at this site are comprised of ferns and trees. This fossil record for this time period in Pennsylvania indicates that the environment was a __________.
A) desert
B) deep ocean
C) shallow sea
D) thriving forest
Chemistry
2 answers:
netineya [11]2 years ago
6 0

Answer:

D) thriving forest

Explanation:

-A desert is a big area with sand that has no vegetation.

-An ocean is a large body of water.

-A shallow sea is a body of salt water that has little depth.

-A forest is an ecosystem that has a lot of vegetation.

According to the definitions and considering that the fossils found are comprised of ferns and trees, the answer is that the environment was a thriving forest.

Andre45 [30]2 years ago
5 0

Answer:

The answer is D)

Explanation:

Clue Words: Ferns and trees.

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You wish to measure the iron content of the well water on the new property you are about to buy. You prepare a reference standar
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Based on Beer-Lambert's Law,

A = εcl ------(1)

where A = absorbance

ε = molar absorptivity

c = concentration

l = path length

Step 1: Calculate the concentration of the diluted Fe3+ standard

Use:

V1M1 = V2M2

M2 = V1M1/V2 = 10 ml*6.35*10⁻⁴M/55 ml = 1.154*10⁻⁴ M

Step 2 : Calculate the concentration of the sample solution

Based on equation (1) we have:

A(Fe3+) = ε(1.154*10⁻⁴)(1)

A(sample) = ε(C)(4.4)

It is given that the absorbances match under the given path length conditions, i.e.

ε(1.154*10⁻⁴)(1) = ε(C)(4.4)

C = 0.262*10⁻⁴ M

This is the concentration of Fe3+ in 100 ml of well water sample

Step 3: Calculate the concentration of Fe3+ in the original sample

Use V1M1 = V2M2

M1 = V2M2/V1 = 100 ml * 0.262*10⁻⁴ M/35 ml = 7.49*10⁻⁵M

Ans: Concentration of F3+ in the well water sample is 7.49*10⁻⁵M


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