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koban [17]
3 years ago
5

If the half-life of C-14 is 5730 years, how much C-14 would be left from a 5000 year-old sample that started as 150 grams?

Chemistry
1 answer:
serious [3.7K]3 years ago
5 0
<h3>Answer:</h3>

81.9 grams

<h3>Explanation:</h3>

From the question we are given;

  • Half-life of C-14 is 5730 years
  • Original mass of C-14 (N₀) = 150 grams
  • Time taken, t = 5000 years

We are required to determine the mass left after 5000 years

  • Using the formula;
  • N = No(1/2)^t/T​, where N is the remaining mass, N₀ is the original mass, t is the time taken and T is the half-life.

   t/T = 5000 yrs ÷ 5730 yrs

    = 0.873

N = 150 g ÷ 0.5^0.873

   = 150 g × 0.546

   = 81.9 g

Therefore, the mass of C-14 left after 5000 yrs is 81.9 g

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8 0
3 years ago
Hno3, a strong acid, is added to shift the ag2co3 equilibrium (equation 7.6) to the right. explain why the shift occurs.
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Answer 1)  When a strong acid like HNO_{3} reacts with Ag_{2} CO_{3} usually the equilibrium shifts to the right because

As per the Le chatelier's principle "if in any reaction, a dynamic equilibrium is disturbed by changing the any of the conditions, the position of equilibrium moves to counteract the change."  So, in the given reaction when HNO_{3} reacts with Ag_{2} CO_{3}  it generates carbon dioxide and water as a by product, if we are adding HNO_{3} it will remove some of the CO_{3} molecule from the reaction mixture, which then tends to shift the equilibrium towards right.

Answer 2) The same would be observed in this case, if we replace HNO_{3} with HCl it will shift the equilibrium to the right as their will be generation of AgCl as the precipitate.

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7 0
3 years ago
For the reaction: CH3NH2(aq) + H2O(aq) ⇌ CH3NH3 +(aq) + OH- Determine the change in the pH (ΔpH) for the addition of 6.7 M CH3NH
Korolek [52]

Answer:

The change in the pH (ΔpH) is 2,17

Explanation:

The reaction:

CH₃NH₂(aq) + H₂O(aq) ⇌ CH₃NH₃⁺(aq) + OH⁻

kb = \frac{[OH^{-}][CH_{3}NH_{3}^+]}{[CH_{3}NH_{2}]} <em>(1)</em>

In equilibrium, a solution of CH₃NH₂ 4,7M produces:

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[CH₃NH₃⁺] = x

[OH⁻] = x

Replacing in (1):

4,38x10^{-4} = \frac{x^2}{4,7-x}

x² + 4,38x10⁻⁴x - 2,0586x10⁻³ = 0

The solutions are:

x = -0,0456 No physical sense. There are not negative concentrations.

x = 0,04515 Real answer.

The concentration of [OH⁻] is 0,04515 M.

As pOH = -log [OH⁻] And pH+pOH = 14. The pH of this solution is:

<em>pH = 12,65</em>

The addition of 6,7M produce this changes in concentrations:

[CH₃NH₂] = 4,656 + x

[CH₃NH₃⁺] = 6,74515 - x

[OH⁻] = 0,04515 - x

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x² - 6,7907x + 0,3025 = 0

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x = 6,74586 No physical sense

x = 0,04484 Real answer.

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Thus ΔpH is 12,65 - 10,49 = <em>2,16 ≈ 2,17</em>

I hope it helps!

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