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2 years ago

The ages of rocks that contain fossils can be determined using the isotope 87Rb. This isotope of rubidium undergoes beta

Chemistry

1 answer:

AVprozaik [17]2 years ago

7 0

Answer:

Age of rock = 722 million years old

Explanation:

Using the formula; fraction remaining = 0.5ⁿ

where n = number of half lives elapsed.

However, from the given values, fraction remaining = 1.000 - 0.0105

fraction remaining = 0.9895

Substituting in the formula to determine the number of half-lives:

0.9895 = 0.5ⁿ

log 0.9895 = n log 0.5

-0.0045842 = -0.30103 n

number of half lives elapsed, n = 0.0152

Therefore age of rock = 0.0152 x 4.75 x 10¹⁰ years = 7.22 x10⁸ years

Age of rock = 722 million years old

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A system receives 575 ) of heat and delivers 425 ) of work. Calculate the change in the internal energy. AE, of the system.

vfiekz [6]

Answer:

ΔE = 150 J

Explanation:

From first law of thermodynamics, we know that;

ΔE = q + w

Where;

ΔE is change in internal energy

q is total amount of heat energy going in or coming out

w is total amount of work expended or received

From the question, the system receives 575 J of heat. Thus, q = +575 J

Also, we are told that the system delivered 425 J of work. Thus, w = -425 J since work was expended.

Thus;

ΔE = 575 + (-425)

ΔE = 575 - 425

ΔE = 150 J

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3 years ago

Classify each of the following as energy primarily transferred as HEAT or energy primarily transferred as WORK.

IgorLugansk [536]

number 1 is work number 2 is heat

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3 years ago

HCl, NaCl, and CO are all examples of chemical properties bonds formulas changes

Ainat [17]

Answer:

HCL, NACL and CO are the examples of chemical formulas

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2 years ago

New questionWhat mass of calcium chloride (CaCl₂) would beproduced from the reaction of 125.9 g of hydrochloriacid (HCI) with ex

marshall27 [118]

Answer:

191.6 g of CaCl₂.

Explanation:

What is given?

Mass of HCl = 125.9 g.

Molar mass of CaCl₂ = 110.8 g/mol.

Molar mass of HCl = 36.4 g/mol.

Step-by-step solution:

First, we have to state the chemical equation. Ca(OH)₂ react with HCl to produce CaCl₂:

$Ca(OH)_2+2HCl\rightarrow CaCl_2+2H_2O.$

Now, let's convert 125.9 g of HCl to moles using the given molar mass (remember that the molar mass of a compound can be found using the periodic table). The conversion will look like this:

$125.9\text{ g HCl}\cdot\frac{1\text{ mol HCl}}{36.4\text{ g HCl}}=3.459\text{ moles HCl.}$

Let's find how many moles of CaCl₂ are being produced by 3.459 moles of HCl. You can see in the chemical equation that 2 moles of HCl reacted with excess Ca(OH)₂ produces 1 mol of CaCl₂, so we state a rule of three and the calculation is:

$3.459\text{ moles HCl}\cdot\frac{1\text{ mol CaCl}_2}{2\text{ moles HCl}}=1.729\text{ moles CaCl}_2.$

The final step is to find the mass of CaCl₂ using the molar mass of CaCl₂. This conversion will look like this:

$1.729\text{ moles CaCl}_2\cdot\frac{110.8\text{ g CaCl}_2}{1\text{ mol CaCl}_2}=191.6\text{ g CaCl}_2.$

The answer would be that we're producing a mass of 191.6 g of CaCl₂.

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1 year ago

How does adding salt to water affect the freezing point

melamori03 [73]

Salt makes the freezing point of water decrease, so it would freeze at a warmer temperature than regular water

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3 years ago