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Alenkinab [10]
2 years ago
11

Select the correct answer from the drop-down menu. a scientist digs up sample of arctic ice that is 458,000 years old. he takes

it to his lab and finds that it contains 1.675 grams of krypton-81. if the half-life of krypton-81 is 229,000 years, how much krypton-81 was present when the ice first formed? use the formula n = n0 . the ice originally contained grams of krypton 81.
Chemistry
1 answer:
Jlenok [28]2 years ago
8 0

The original mass of krypton 81 that is present in the ice is 6.70 grams.

<h3>How do we calculate original mass?</h3>

Original mass of any substance will be calculated as below for the decomposition reaction is:

N = N₀(1/2)ⁿ, where

N = remaining mass of krypton-81 = 1.675g

N₀ = original mass of krypton-81 = ?

n will be calculated as:
n = T/t, where

T = total time period = 458,000 years

t = half life time = 229,000 years

n = 458,000/229,000 = 2

Now putting all these values on the above equation, we get

N₀ = 1.675 / (1/2)²

N₀ = 6.70 g

Hence required mass is 6.70 g.

To know more about half life time, visit the below link:
brainly.com/question/2320811

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How many moles are in 29.5 grams of Ax?
JulsSmile [24]

The number of moles present in 29.5 grams of argon is 0.74 mole.

The atomic mass of argon is given as;

Ar = 39.95 g/mole

The number of moles present in 29.5 grams of argon is calculated as follows;

39.95 g ------------------------------- 1 mole

29.5 g ------------------------------ ?

= \frac{29.5}{39.95} \\\\= 0.74 \ mole

Thus, the number of moles present in 29.5 grams of argon is 0.74 mole.

<em>"Your question seems to be missing the correct symbol for the element" </em>

Argon = Ar

Learn more here:brainly.com/question/4628363

6 0
2 years ago
What are the empirical and molecular formulas of a hydrocarbon if combustion of 2.10 g of the compound yields 6.59 g co2 and 2.7
mariarad [96]

 The  empirical  formula    of hydrocarbon is  CH2

The  molecular formula  of the  hydrocarbon is  C6H12


    <u><em>Explanation</em></u>

Hydrocarbon  is  made up  of carbon and hydrogen


<h3><u><em> </em></u>Empirical formula  calculation</h3>

 Step 1:  find  the  moles   CO2  and  H2O

moles =mass/molar mass

moles   of CO2 =  6.59 g/ 44 g/mol = 0.15 moles

moles of H2O = 2.70 g / 18 g/mol =  0.15  moles

Step 2: Find the moles  ratio  of Co2:H2O  by diving  each mole by smallest mole(0.15)

that  is  for  CO2 = 0.15/0.15  =1

              For H2O = 0.15/0.15 =1

therefore  the mole ratio  of Co2 : H2O = 1:1  which  implies that 1 mole of Co2  and 1  mole of H2O is  formed  during combustion reaction.


From the  the law of mass conservation the number  of atoms in reactant side  must  be equal to  number of  atoms  in product side

therefore  since  there 1 atom  of C  in product side there  must be 1 atom of C  in reactant  side.

In addition  there is 2 H atom in product  side  which should be the  same  in reactant side.  

From information above the empirical formula is therefore = CH2


Molecular formula  calculation

[CH2}n= 84 g/mol

[12+ (1x2)] n = 84 g/mol

14 n =  84 g/mol

n = 6

multiply the  each subscript  in CH2  by  6

 Therefore the molecular formula = C6H12




5 0
3 years ago
Why does no reaction occur when mixing magnesium nitrate and lithium bromide?
mixas84 [53]

Answer:

yahh

Explanation:

a precipitation reaction is a reaction that yields an insoluble product—a precipitate—when two solutions are mixed.

3 0
2 years ago
Which of the following units would be the most appropriate for measuring the thickness of a piece of paper? A. centimeters B. mi
Alla [95]
B, millimeters because paper is really thin therefore it'd require small measurements for units.
3 0
3 years ago
The Law of Superposition states that
SCORPION-xisa [38]
<span>C. older material is located below younger material 
</span>
8 0
2 years ago
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