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Alenkinab [10]
3 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]3 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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Calculate the missing variables in each experiment below using Avogadro’s law.
blagie [28]

Answer:

The answer to your question is: letter c

Explanation:

Data

V1 = 612 ml    n1 = 9.11 mol

V2 = 123 ml    n2 = ?

Formula

                               \frac{V1}{n1}  =  \frac{V2}{n2}

                                         n2 = \frac{n1V2}{V1}

                                         n2 = \frac{(9.11)((123)}{(612)}

                                                n2 = 1.83 mol                                                

5 0
3 years ago
Here's the question ~
Lelechka [254]

Using the Rydberg formula, the spectral line of H - atom is suitable for this purpose is Paschen, ∞ → 3.

  • Using the Rydberg formula;

1/λ = RH(1/nf^2 - 1/ni^2)

Given that;

λ = wavelength

RH = Rydberg constant

nf = final state

ni = initial state

  • When final state = 3 and initial state = ∞

Then;

1/λ =  1 × 10^7 m-1 (1/3^2 - 1/ ∞^2)

1/λ =  1 × 10^7 m-1 (1/3^2 )

λ = 900 nm

Hence, the correct answer is Paschen, ∞ → 3

Learn more about the Rydberg formula; brainly.com/question/17753747

3 0
2 years ago
Read 2 more answers
9. Describe two ways in which you can conserve and recycle lab resources.<br> I
Law Incorporation [45]

Answer:

Using solar energy, hydroelectric energy and wind are major ways of conserving natural resources. Trees and other organic energy sources are traditional sources of renewable energy. Forests can be replanted and hemp and other organic materials such as ethanol can be used to preserve natural resources.

4 0
3 years ago
1)
Delicious77 [7]

Answer:

<u><em></em></u>

  • <u><em>C) How much energy was added to the substance to increase molecule motion? </em></u>

Explanation:

<em>The most relevant question to ask regarding this change</em> must take into account the physical knowledge about matter.

When matter changes from<em> liquid </em>state to <em>gaseous</em> state, a physical change called evaporation, the particles (molecules or atoms) of the <em>pure substance </em>will separate from each other, take up more space and move faster.

<em>Condensation</em> is the opposite to evaporation, thus the option A) is not the most relevant question.

<em>The charge of the particles</em> does not change; so the option B) is not relevant at all.

The particles should gain energy from the surroundings to <em>increase</em> their <em>motion</em> (kinetic energy) when they pass from liquid state, where they move slower, to gas state, where they move faster. Hence, the option<em> C), How much energy was added to the substance to increase molecule motion?</em> , is totally relevant.

Since this is an increase in the <em>kinetic energy of the molecules</em>, the option D) is not relevant.

6 0
3 years ago
Calculate the pH of the solutions: [H^+]= 1.6 x 10^-3 M
Yuliya22 [10]

Answer:

A) pH = 2.8

B) pH = 5.5

C) pH = 8.9

D) pH = 13.72

Explanation:

a) [H⁺]  = 1.6 × 10⁻³ M

pH = -log [H⁺]

pH = -log [1.6 × 10⁻³ ]

pH = 2.8

b) [H⁺]  = 3 × 10⁻⁶

pH = -log [H⁺]

pH = -log [3 × 10⁻⁶ ]

pH = 5.5

c) [OH⁻] = 8.2 × 10⁻⁶

pOH = -log[OH]

pOH = -log[8.2 × 10⁻⁶]

pOH = 5.1

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 5.1

pH = 8.9

d) [OH⁻] = 0.53 M

pOH = -log[OH]

pOH = -log[0.53]

pOH = 0.28

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 0.28

pH = 13.72

5 0
3 years ago
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