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Svetlanka [38]
2 years ago
13

Element X is a radioactive isotope such that every 51 years, its mass decreases by half. Given that the initial mass of a sample

of Element X is 7500 grams, how long would it be until the mass of the sample reached 6900 grams, to the nearest tenth of a year?
Mathematics
1 answer:
pychu [463]2 years ago
5 0

Answer: It will take 6 years for 7500 grams of X to reach 6900 grams.

Step-by-step 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

a = let initial amount of the reactant  

a - x = amount left after decay process  

a) 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.

51=\frac{0.69}{k}

k=\frac{0.69}{51}=0.0135years^{-1}

b) for  7500 g to reach to 6900 g

t=\frac{2.303}{0.0135}\log\frac{7500}{6900}

t=6years

It will take 6 years for 7500 grams of X to reach 6900 grams.

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Week 1 2 3 4 5 Water Level (inches) − 1 1 4 1 3 8 2 1 2 − 1 5 8 − 1 3 4 Between which two weeks did the water level change the m
suter [353]

Answer:

The water level change the most in week 3 and week 4

The change = -370 inches

Step-by-step explanation:

Given - Week                              1           2            3           4            5

             Water Level (inches) − 1 1 4     1 3 8      2 1 2      -1 5 8      -1 3 4

To find - Between which two weeks did the water level change the most? Calculate the change .

Proof -

The formula for change in water level with respect to week be-

Rate of Change in Water Level = Difference in water level / Difference in weeks

Now,

For week 1 and week 2

Rate of change in water level = \frac{138 - 114}{2 - 1} = \frac{24}{1} = 24 inches

Now,

For week 1 and week 3

Rate of change in water level = \frac{212 - 114}{3 - 1} = \frac{98}{2} = 49 inches

Now,

For week 1 and week 4

Rate of change in water level = \frac{-158 - 114}{4 - 1} = -\frac{272}{3} = -90.67 inches

Now,

For week 1 and week 5

Rate of change in water level = \frac{-134 - 114}{5 - 1} = -\frac{248}{4} = -62 inches

Now,

For week 2 and week 3

Rate of change in water level = \frac{212 - 138}{3 - 2} = \frac{74}{1} = 74 inches

Now,

For week 2 and week 4

Rate of change in water level = \frac{-158 - 138}{4 - 2} = -\frac{296}{2} = -148 inches

Now,

For week 2 and week 5

Rate of change in water level = \frac{-134 - 138}{5 - 2} = -\frac{272}{3} = -90.67 inches

Now,

For week 3 and week 4

Rate of change in water level = \frac{-158 - 212}{4 - 3} = -\frac{370}{1} = -370 inches

Now,

For week 3 and week 5

Rate of change in water level = \frac{-134 - 212}{5 - 3} = -\frac{346}{2} = 173 inches

Now,

For week 4 and week 5

Rate of change in water level = \frac{-134 + 158}{5 - 4} = \frac{24}{1} = 24 inches

∴ we get

The water level change the most in week 3 and week 4

The change = -370 inches

Note :

The highest change means which temperature goes the most change in water level. It can be negative also.

So, We have to take the modulus and then find the highest number.

Here, 370 > 173

So, Highest change occurs in Week 3 and Week 4 but not in Week 3 and Week 5.

7 0
2 years ago
7m + 3mn when m = 8 and n = 14
Kazeer [188]

Answer:

392

Step-by-step explanation:

m = 8 and n = 14

Substituting the values of m and n in the question, we get :

7m + 3mn

=( 7 x 8) +(3 x 8 x 14)

= 56 + 336

= 392

8 0
3 years ago
Read 2 more answers
You know that 60% of students in a school are participating in a fundraiser. If between 200 and 400 students are participating,
allsm [11]
So i think in the school there may be 4800 in the school. Hope this helps
8 0
2 years ago
Megan charges %5.00 for each hour, (h), she babysits. Last week, the total amount she earned by babysitting was $65.00.
mel-nik [20]

Answer:

B

Step-by-step explanation:

To find how many hours she worked you must divide $65 by $5 and B is the only equation where you can do that.

8 0
2 years ago
Help please!! Show work if possible!
Natasha2012 [34]

Answer:

Please see the attached pictures for full solution.

5 0
3 years ago
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