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valentinak56 [21]
2 years ago
8

A radioactive substance decays exponentially. a scientist begins with 120 milligrams of a radioactive substance. after 14 hours,

60 mg of the substance remains. how many milligrams will remain after 19 hours?
Chemistry
1 answer:
Yanka [14]2 years ago
4 0
First thing is you have to find the half life of the substance. The half life equation is
Final Mass = Initial Mass * 0.5^(time/time per half life)
Now we substitute the values given and we get
60 mg = 120 * 0.5^(14/t)
Solve for t and you get
t = 14 hours
Now plug 19 into the equation
Final Mass = 120 * 0.5^(19/14)
Final Mass = 46.84 mg
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Concentration can be expressed in different forms: molarity, molality, normality, percentage, part per million and many more. For molality, it is a unit of concentration expressed as moles of solute per kilogram of solvent. Therefore,

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3 years ago
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What is the molar solubility of MgF2 in a 0.36 M Mg(NO3)2 solution? For MgF2, Ksp = 8.4 × 10^–8
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Answer:

2.4 × 10⁻⁴ M

Explanation:

Step 1: Calculate the concentration of Mg²⁺ coming from Mg(NO₃)₂

Mg(NO₃)₂ is a strong electrolyte and the molar ratio of Mg(NO₃)₂ to Mg²⁺ is 1:1. The initial molar concentration of Mg²⁺ is 1/1 × 0.36 M = 0.36 M.

Step 2: Make an ICE chart for the solution of MgF₂

        MgF₂(s) ⇄ Mg²⁺(aq) + 2 F⁻(aq)

I                           0.36             0

C                           +S             +2S

E                         0.36+S         2S

The solubility product constant is:

Ksp = [Mg²⁺] × [F⁻]² = (0.36+S) × (2S)²

Since S <<< 0.36, 0.36+S ≈ 0.36.

Ksp = 0.36 × 4S² = 8.4 × 10⁻⁸

S = 2.4 × 10⁻⁴ M

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2. The glassware is then soaked overnight in warm soap solution.

3. Then before rinsing with tap water, the glassware are scrubbed with an appropriate brush.

4. After scrubbing, the glassware is rinsed thoroughly with tap water in order to make sure there are no traces of soap solution.

5. The glassware is then rinsed with de-ionized water and finally with the solution that would be used for the volumetric measurement.

6 0
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In NMR if a chemical shift(δ) is 211.5 ppm from the tetramethylsilane (TMS) standard and the spectrometer frequency is 556 MHz,
Vika [28.1K]

Answer:

The answer is: 11759 Hz

Explanation:

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In NMR spectroscopy, the chemical shift (δ), expressed in ppm, of a given nucleus is given by the equation:

\delta (ppm) = \frac{Observed\,frequency (Hz)}{Frequency\,\, of\,\,the\,Spectrometer (MHz)} \times 10^{6}

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<u>Therefore, the signal is at 11759 Hz from the TMS.</u>

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