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mihalych1998 [28]
3 years ago
10

Chromium-51 has a half life of 27.70 days. How much will be left after 166.2 days if

Chemistry
1 answer:
Svet_ta [14]3 years ago
8 0

Answer:

Decayed mass: 909.56 g, Left mass: 14.44 g.

Explanation:

The time constant of the Chromium-51 is:

\tau = \frac{t_{1/2}}{\ln 2}

\tau = \frac{27.70\,days}{\ln 2}

\tau = 39.963\,days

The decay equation for the isotope has the following form:

\frac{m(t)}{m_{o}} = e^{-\frac{t}{\tau} }

The total decay at a given instant t is:

\% \delta = \left(1-e^{-\frac{t}{\tau} } \right) \times 100\,\%

The total decay at 166.2 days is:

\% \delta = 98.437\,\%

Decayed mass: 909.56 g, Left mass: 14.44 g.

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Given the following balanced equation at 120°C: A(g) + B(g) ⇋ 2 C(g) + D(s)(a) At equilibrium a 4.0 liter container was found to
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Answer:

a) kc = 0,25

b) [A] = 0,41 M

c) [A] = <em>0,8 M</em>

[B] =<em>0,2 M</em>

[C] = <em>0,2M</em>

Explanation:

The equilibrium-constant expression is defined as the ratio of the concentration of products over concentration of reactants. Each concentration is raised to the power of their coefficient.

Also, pure solid and liquids are not included in the equilibrium-constant expression because they don't affect the concentration of chemicals in the equilibrium.

If global reaction is:

A(g) + B(g) ⇋ 2 C(g) + D(s)

The kc = \frac{[C]^2}{[A][B]}

a) The concentrations of each compound are:

[A] = \frac{1,60 moles}{4,0 L} = <em>0,4 M</em>

[B] = \frac{0,40 moles}{4,0 L} = <em>0,1 M</em>

[C] = \frac{0,40 moles}{4,0 L} = <em>0,1 M</em>

<em>kc = </em>\frac{[0,1]^2}{[0,4][0,1]} = 0,25

b) The addition of B and D in the same amount will, in equilibrium, produce these changes:

[A] = \frac{1,60-x moles}{4,0 L}

[B] = \frac{0,60-x moles}{4,0 L}

[C] = \frac{0,60+2x moles}{4,0 L}

0,25 = \frac{[0,60+2x]^2}{[1,60-x][0,60-x]}

You will obtain

3,75x² +2,95x +0,12 = 0

Solving

x =-0,74363479081119   → No physical sense

x =-0,043031875855476

Thus, concentration of A is:

\frac{1,60-(-0,04 moles)}{4,0 L} = <em>0,41 M</em>

c) When volume is suddenly halved concentrations will be the concentrations in equilibrium over 2L:

[A] = \frac{1,60 moles}{2,0 L} = <em>0,8 M</em>

[B] = \frac{0,40 moles}{2,0 L} = <em>0,2 M</em>

[C] = \frac{0,40 moles}{2,0 L} = <em>0,2M</em>

I hope it helps!

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