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4 years ago

explain how fossils and other materials can tell us about the conditions of an area at the time it existed.

1 answer:

3 0

Well, if the fossil is from the sea/is an ocean animal (for example a fish) , then you can say that the land was once underwater. If the fossil is from a desert, you can say that the land was once a desert, etc.

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You are given a sample of limestone, which is mostly CaCO3, to determine the mass percentage of Ca in the rock. You dissolve the

irakobra [83]

Answer:

34.15% is the mass percentage of calcium in the limestone.

Explanation:

Mass of precipitate that is calcium oxalate = 140.2 mg = 0.1402 g

1 mg = 0.001 g

Moles of calcium oxalate = $\frac{0.1402 g}{128 g/mol}=0.001095 mol$

1 mole of calcium oxalate have 1 mole of calcium atom.

Then 0.001095 moles of calcium oxalate will have 0.001095 moles of calcium atom.

Mass of 0.001095 moles of calcium :

0.001095 mol × 40 g/mol = 0.04381 g

Mass of sample of limestone = 128.3 mg = 0.1283 g

Percentage of calcium in limestone:

$\frac{0.04381 g}{0.1283 g}\times 100=34.15\%$

34.15% is the mass percentage of calcium in the limestone.

7 0

3 years ago

Read 2 more answers

Which form of oxygen (solid,liquid or gas) would have the highest temperature

ElenaW [278]

Answer:

drip drip water splash (gas)

Explanation:

8 0

3 years ago

Use the formula: PV=nRT<br><br> If P=12, V=22.4, R=.0821 and T=100, then what would n=?

Lina20 [59]

$PV=nRT \\ (12)(22.4)=n(.0821)(100) \\ 268.8=8.21n \\ 268.8/8.21=8.21n/8.21 \\ n=32.74$
n ≈ 32.74
Hope this helps!

7 0

3 years ago

An unknown compound contains only carbon, hydrogen, nitrogen, and oxygen. Complete combustion of a 2.77 g sample of the compound

alisha [4.7K]

The molecular formula of the unknown compound is determined as C₉H₁₁NO₂.

<h3>Molecular formula of the compound</h3>

The molecular formula is calculated as follows;

CHNO + O₂ ------------> CO₂ + H₂O

Mass of carbon, C: = (6.64 x 12)/44 = 1.81 g in 2.77 g sample

Mass of hydrogen, H: = (1.67 x 2)/18 = 0.186 g in 2.77 g sample

Mass of Nitrogen, N: = (2.77 x 0.143)/1.69 = 0.234 g

Mass of oxygen, O: = 2.77 g - 1.81 g - 0.186 g - 0.234 g = 0.54 g

<h3>molar ratio of the elements: </h3>

C = 1.81 g = 0.15 mol

H = 0.186 g = 0.186 mol

N = 0.234 g = 0.017 mol

O = 0.54 g = 0.0337 mol

divide through with the smallest number of moles (0.017 mol);

C = 9

H = 11

N = 1

O = 2

Molecular formula = C₉H₁₁NO₂

Check the molar mass of the compound = (9 x 12) + (11 x 1) + (14) + (2 x 16) = 165 g/mol

Thus, the molecular formula of the unknown compound is determined as C₉H₁₁NO₂.

Learn more about molecular mass here: brainly.com/question/21334167

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4 0

2 years ago

Helllllp me please <br> Part D ends with neon Express your answer as an integer. 20

marysya [2.9K]

Answer:

attach file please

3 0

3 years ago