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vovikov84 [41]
2 years ago
14

A sample of cobalt-60 (t₁/₂= 5.27 yr), a powerful g emitter used to treat cancer, was purchased by a hospital on March 1, 2012.

The sample must be replaced when its activity reaches 70.% of the original value. On what date must it be replaced?
Chemistry
1 answer:
Bad White [126]2 years ago
8 0

The  sample of cobalt-60 (t₁/₂= 5.27 yr) must be replaced after 2.7 years which makes 2 years and 8.4 months. if the sample was purchased on march 2012 then it must be replaces on mid January 2015.

<h3>Briefly explained</h3>

To determine when the cobalt 60 needs to be replaced when it has achieved 70% of the activity. We simply need to use the first order integrated rate law which will allow us to calculate the time. However, when using this equation we need the Decay constant for Cobalt 60, which we can get from the half life of Cobalt 60.

We simply divide the half life of 5.27 years into the natural log of two and we get .13151 over years. If we have reached 70 Then 70% expressed as a decimal .7. So we have .7 of an original amount of one. So you can think of this as being divided by one. So the natural log of the amount at time T divided by the original amount is equal to negative K. Which we just calculated, multiplied by T.

With some algebraic rearrangement we get 2.7 years. So 2.7 years from the purchase of March one in 2012 is approximately early 2015.

Learn more about decay

brainly.com/question/1898040

#SPJ4

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A sample of the chiral molecule limonene is 79% enantiopure. what percentage of each enantiomer is present? what is the percent
Degger [83]

Answer :  The % of (+) limonene isomer = 79%


                The % of (-) limonene isomer = 0%


                The % of enantiomeric excess = 58%


Explanation :   Enantiomeric excess (ee) is the measurement of purity used for chiral substances.


Given,


% of pure limonene enantiomer = The % of (+) limonene isomer = 79%


Therefore, The % of (-) limonene isomer = 0%


Formula used :  

\%(+)\text{ isomer}=\frac{ee}{2}+50\%


Where,         ee → enantiomeric excess


Now, put all the values in above formula, we get the value of enantiomeric excess (ee).


     {ee}=\frac{\%(+)-50\%}{2}


            =\frac{79\%-50\%}{2}


              = 58%



7 0
3 years ago
Read 2 more answers
At constant pressure, which of these systems do work on the surroundings? A ( s ) + B ( s ) ⟶ C ( g ) A(s)+B(s)⟶C(g) 2 A ( g ) +
Tju [1.3M]

Correct question:

At constant pressure, which of these systems do work on the surroundings?

(a) A ( s ) + B ( s ) ⟶ C ( g )

(b) 2 A ( g ) + 2 B ( g ) ⟶ 5 C ( g )

(c) A ( g ) + B ( g ) ⟶ C ( g )

(d) 2 A ( g ) + 2 B ( g ) ⟶ 3 C ( g )

Answer:

(a) A ( s ) + B ( s ) ⟶ C ( g )

(b) 2 A ( g ) + 2 B ( g ) ⟶ 5 C ( g )

Explanation:

Work done by a system on the surroundings at a constant pressure is given as;

W = -PΔV

Where;

ΔV is gas expansion, that is final volume of the gas minus initial volume of the gas must be greater than zero.

Part (a)

A ( s ) + B ( s ) ⟶ C ( g )

ΔV = 1 - (0) = 1 (expansion)

Part (b)

2 A ( g ) + 2 B ( g ) ⟶ 5 C ( g )

ΔV = 5 - ( 2+ 2) = 1 (expansion)

Part (c)

A ( g ) + B ( g ) ⟶ C ( g )

ΔV = 1 - ( 1 + 1) = -1 (compression)

Part (d)

2 A ( g ) + 2 B ( g ) ⟶ 3 C ( g )

ΔV = 3 - ( 4) = -1 (compression)

Thus, systems where there is gas expansion are in part (a) and part (b). The correct answers are:

(a) A ( s ) + B ( s ) ⟶ C ( g )

(b) 2 A ( g ) + 2 B ( g ) ⟶ 5 C ( g )

4 0
3 years ago
The isomers butane and methyl propane have
madreJ [45]

Explanation:

“The isomers butane and methyl propane have the same molecular formula and different properties”, this is because structural isomers usually have different properties to their parent.

3 0
3 years ago
Sophia was fascinated while studying the role of oceans in the hydrosphere. She decided to illustrate the features of the ocean
ANEK [815]

Answer:

The Major features of the ocean floor are:

  1. Continental Shelf
  2. Continental Slope
  3. Continental Rise
  4. Abyssal Plain
  5. Oceanic Trench
  6. Mid-Ocean Ridge

Explanation:

1. Continental Shelf: This refers to the part of the land on every continent that is covered with water that is not too deep. The types of animals that can be found on the continental shelf are:

Crab, Tuna, Lobster, Dungeness cod, etc. Within the Continental shelf, there are permanent rocks that house other organisms such as sponges, anemones, clams, sponges, oysters. The continental shelf also contains the route of migration for bigger animals such as sea turtles dolphins and even whales.

2. Continental Slope: This spans from the shelf break to the continental rise.  It can slope up to 4 degrees. Slopes can be created by faulting, slumping of huge boulders of sediments, rifting, etc.

Some of the aquatic animals that can be found in this region include but are not limited to:

Sablefish, Dover sole rockfish, etc.

3. Continental rise

This part of the ocean floor usually has a very steep gradient or angle slope. It slopes very steeply into the abyssal plain of the ocean.

The following can help form continental rise:

  • Mass wasting;
  • deposition from contour currents and
  • the longitudinal settling of biogenic and clastic particles

4. Abyssal Plain.

This is the real bottom of the ocean. There is a very high probability that one would find animals such as nematodes, polychaetes, etc which are all types of worms down there. The Abyssal plain is also home to molluscs,  and echinoderms.

5. Oceanic Trench

Sometimes there is a long and narrow indenture or depression along the seafloor. These are called Trenches. Trenches are sometimes formed by the boundaries between one lithospheric plate and another. The deepest trench on earth is found in the Pacific Ocean. It has been nick-named the Challenger Deep and said to be the deepest point known on earth reaching almost 11 kilometers.

6. Mid-Ocean Ridge

This is a mountain range underneath the ocean. It is formed when there is an upward push by convection currents of the mantle beneath the oceanic crust. When this happens and molten magma is ejected or created at the boundary between the plates, the result is a Mid-Oceanic Ridge.

Cheers

7 0
2 years ago
Valeric acid, HC5H9O2 (Ka = 1.5 ✕ 10−5), is used in the manufacture of magnesium valerate, a nerve-calming agent. What is the hy
Studentka2010 [4]

Answer:

[H^+]=0.00332M

Explanation:

Hello,

In this case, considering the dissociation of valeric acid as:

HC_5H_9O_2 \rightleftharpoons C_5H_9O_2 ^-+H^+

Its corresponding law of mass action is:

Ka=\frac{[H^+][C_5H_9O_2^-]}{[HC_5H_9O_2]}

Now, by means of the change x due to dissociation, it becomes:

Ka=\frac{(x)(x)}{0.737-x}=1.5x10^{-5}

Solving for x we obtain:

x=0.00332M

Thus, since the concentration of hydronium equals x, the answer is:

[H^+]=x=0.00332M

Best regards.

7 0
3 years ago
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