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Travka [436]
4 years ago
14

Strontium-90 is a radioisotope that will decrease in mass by one-half every 29 years. How many years will it take for a 10.0-gra

m sample of strontium-90 to decay to 5.00 grams?
Chemistry
1 answer:
Lelechka [254]4 years ago
7 0

Answer: It will take 29 years for a 10.0-gram sample of strontium-90 to decay to 5.00 grams

Explanation:

Radioactive decay process is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations. The radioactive decay follows first order kinetics.

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

Half life is represented by t_{\frac{1}{2}

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

\lambda = rate constant

Given : Strontium-90 decreases in mass  by one-half every 29 years , that is half life of Strontium-90  is 29 years.

As half life is independent of initial concentration, it will take 29 years for a 10.0-gram sample of strontium-90 to decay to 5.00 grams as the amount gets half.

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commercial cold packs consist of solid NH4NO3 and water. In a coffee-cup calorimeter, 5.60g NH4NO3 is dissolved in 100g of water
fgiga [73]

Answer:

-1.37 kJ/mol

Explanation:

The expression for the calculation of the enthalpy of dissolution of [tex[NH_4NO_3[/tex] is shown below as:-

\Delta H=m\times C\times \Delta T

Where,  

\Delta H  is the enthalpy of dissolution of [tex[NH_4NO_3[/tex]

m is the mass

C is the specific heat capacity

\Delta T  is the temperature change

Thus, given that:-

Mass of ammonium nitrate = 5.60 g

Specific heat = 4.18 J/g°C

\Delta T=17.9-22.0\ ^0C=-4.1\ ^0C

So,  

\Delta H=-1.25\times 4.18\times 3.9\ J=-95.9728\ J

Negative sign signifies loss of heat.  

Also, 1 J = 0.001 kJ

So,  

\Delta H=-0.096\ kJ

Also,

Molar mass of [tex[NH_4NO_3[/tex] = 80.043 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

Moles= \frac{5.60\ g}{80.043 \ g/mol}

Moles= 0.06996\ mol

Thus, \Delta H=-\frac{0.096}{0.06996}\ kJ/mol=-1.37\ kJ/mol

6 0
4 years ago
8. A train travels at a at a speed of 30 miles per hour if 1 mile = 1.6 kilometers, how fast is the train traveling in kilometer
sattari [20]

Answer:

Explanation:

A: 0.8 KM/Min

1.6 x 30 = 48

48/60 = 0.8

3 0
3 years ago
What does it mean when a wave's amplitude increases?
anastassius [24]

Answer:

It becomes shorter

Explanation:

A wave, such as a Soundwave, controls volume based on it's Wavelength. A Louder sound has a shorter wavelength, a softer sound has it's waves spread out more. Amplitude is simply a fancy name for Volume in Amps. When amplitude increases, the volume increases. Thus, waves become shorter.

7 0
4 years ago
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30 POINTS
Pavlova-9 [17]
Because neither can be created or destroyed
7 0
3 years ago
Water alone does not easily remove grease from dishes or hands because grease is nonpolar and water is polar. The addition of so
rewona [7]

Answer:

Micelle Formation

Explanation:

The soap molecule has a nonpolar and a polar cationic end when it is dissolved in water. When it dissolves in water, the sodium stearate congregates to form small spheres (called micelles) with the on the inside and the on the surface. The anionic end can attract and interacts with the polar water molecules, while the interact with the nonpolar grease. This allows the soapy water to remove the grease by trapping the grease inside the micelle.

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3 years ago
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