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Serga [27]
3 years ago
12

To determine the absolute age of rocks and fossils, geologists use _____.

Chemistry
1 answer:
Pavlova-9 [17]3 years ago
7 0

Answer:

The rates of decay of radioactive elements

Explanation:

The age of a rock in years is called its absolute age. Geologists find absolute ages by measuring the amount of certain radioactive elements in the rock. When rocks are formed, small amounts of radioactive elements usually get included.

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For an alloy that consists of 91.0 g copper, 111 g zinc, and 7.51 g lead, what are the concentrations (a) of Cu (in at%), (b) of
viktelen [127]

Answer:

\% Cu=45.2\%\\\\\% Zn=53.6\%\\\\\% Pb=1.2\%

Explanation:

Hello!

In this case, given the masses of copper, zinc and lead, it is possible to compute the moles via their atomic masses first:

n_{Cu}=\frac{91.0gCu}{63.55g/mol}=1.432mol\\\\ n_{Zn}=\frac{111gZn}{65.41g/mol}=1.697mol\\\\n_{Pb}=\frac{7.51gPb}{207.2g/mol}=0.0362mol\\

Now, we compute the atomic percentages as shown below:

\% Cu=\frac{1.432}{1.432+1.697+0.0362}*100\% =45.2\%\\\\\% Zn=\frac{1.697}{1.432+1.697+0.0362}*100\%=53.6\%\\\\\% Pb=\frac{0.0362}{1.432+1.697+0.0362}*100\%=1.2\%

Best regards!

4 0
3 years ago
A sample of an unknown compound with a mass of 0.847 g has the following composition: 50.51 % fluorine and 49.49 % iron. When th
sergejj [24]

Answer: 0,4278g of F and 0,4191g of Fe

Explanation: it's possible to calculate the mass of each element by multiplying the percentage (decimal) of the element by the mass of the compound.

For Fluorine (F)

0,847g * 0,5051 = 0,4278g of F

For iron (Fe)

0,847 * 0,4949 = 0,4191g of Fe

This is determined because even when the compound is decomposed, due to conservative law of mass, the decomposition process do not affect the amount of matter, so the mass of the elements remain even if they are separated from the original molecule.

At the end, the sum of the elements masses should be the total mass of the compound.

4 0
3 years ago
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Question 22
Mrrafil [7]
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3 0
2 years ago
Each cell has a membrane. This is a thin layer that surrounds it. It keeps the inside and outside of the cell separate. What doe
viktelen [127]

Answer:

D

Explanation:

Cell membrane, also called plasma membrane, thin membrane that surrounds every living cell, delimiting the cell from the environment around it.

3 0
4 years ago
Read 2 more answers
An object with a mass of 5.6 g raises the level of water in a graduated cylinder from 25.1 mL to 33.9 mL. What is the density of
kondor19780726 [428]

Answer:

0.6364 g/cm^3

Explanation:

Density = mass/volume

Where mass = 5.6g and...

Volume = (33.9 - 25.1) = 8.8ml

Where 1ml = 1 cm^3

Density = 5.6/8.8 = 0.6364 g/cm^3

6 0
3 years ago
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