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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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1) Electron

Explanation:

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Digiron [165]
<h3>1</h3>

Species shown in bold are precipitates.

  • Ca(NO₃)₂ + 2 KOH → Ca(OH)₂ + 2 KNO₃
  • Ca(NO₃)₂ + Na₂C₂O₄ → CaC₂O₄ + 2 NaNO₃
  • Cu(NO₃)₂ + 2 KI → CuI₂ + 2 KI
  • Cu(NO₃)₂ + 2 KOH → Cu(OH)₂ + 2 KNO₃
  • Cu(NO₃)₂ + Na₂C₂O₄ → CuC₂O₄ + 2 NaNO₃
  • Ni(NO₃)₂ + 2 KOH → Ni(OH)₂ + 2 KNO₃
  • Ni(NO₃)₂ + Na₂C₂O₄ → NiC₂O₄ + 2 NaNO₃
  • Zn(NO₃)₂ + 2 KOH → Zn(OH)₂ + 2 KNO₃
  • Zn(NO₃)₂ + Na₂C₂O₄ → ZnC₂O₄ + 2 NaNO₃

<h3>2</h3>

A double replacement reaction takes place only if it reduces in the concentration of ions in the solution. For example, the reaction between Ca(NO₃)₂ and KOH produces Ca(OH)₂. Ca(OH)₂ barely dissolves. The reaction has removed Ca²⁺ and OH⁻ ions from the solution.

Some of the reactions lead to neither precipitates nor gases. They will not take place since they are not energetically favored.


<h3>3</h3>

Compare the first and last row:

Both Ca(NO₃)₂ and Zn(NO₃)₂ react with KOH. However, between the two precipitates formed, Ca(OH)₂ is more soluble than Zn(OH)₂.

As a result, add the same amount of KOH to two Ca(NO₃)₂ and Zn(NO₃)₂ of equal concentration. The solution that end up with more precipitate shall belong to Zn(NO₃)₂.


<h3>4</h3>

Compare the second and third row:

Cu(NO₃)₂ reacts with KI, but Ni(NO₃)₂ does not. Thus, add equal amount of KI to the two unknowns. The solution that forms precipitate shall belong to Cu(NO₃)₂.

8 0
3 years ago
You have just isolated a new radioactive element. If you can determine its half-life, you will win the Nobel Prize in physics. Y
lbvjy [14]

Answer: 2.58 days

Explanation:

Expression for rate law for first order kinetics is given by:

t=\frac{2.303}{k}\log\frac{a}{a-x}

where,

k = rate constant  = ?

t = age of sample  = 6 days

a = initial amount of the reactant  =  1 g

a - x = amount left after decay process   = 0.2 g

a) to find the rate constant

6=\frac{2.303}{k}\log\frac{1.0}{0.2}

k=\frac{2.303}{6}\log\frac{1.0}{0.2}

k=0.268days^{-1}

b) for completion of half life:  

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

t_{\frac{1}{2}}=\frac{0.693}{k}

t_{\frac{1}{2}}=\frac{0.693}{0.268}=2.58days

The half life is 2.58 days

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3 years ago
For the gas phase decomposition of 1-bromopropane, CH3CH2CH2BrCH3CH=CH2 + HBr the rate constant at 622 K is 6.43×10-4 /s and the
ladessa [460]

<span>Answer is: activation energy of this reaction is 212,01975 kJ/mol.
Arrhenius equation: ln(k</span>₁/k₂) = Ea/R (1/T₂ - 1/T₁<span>).
k</span>₁<span> = 0,000643 1/s.
k</span>₂ = 0,00828 1/s.

T₁ = 622 K.

T₂ = 666 K.

R = 8,3145 J/Kmol.

1/T₁<span> = 1/622 K = 0,0016 1/K.
1/T</span>₂<span> = 1/666 K = 0,0015 1/K.
ln(0,000643/0,00828) = Ea/8,3145 J/Kmol · (-0,0001 1/K).
-2,55 = Ea/8,3145 J/Kmol · (-0,0001 1/K).
Ea = 212019,75 J/mol = 212,01975 kJ/mol.</span>

4 0
3 years ago
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