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masya89 [10]
2 years ago
5

A 200-gram sample of a radioactive nuclide is left to decay for 60 hours. At the end of 60 hours, only 25 grams of the sample is

left. What is the half-life of the nuclide sample?
60 hours
30 hours
40 hours
20 hours ---> I think 20??
Chemistry
1 answer:
Goryan [66]2 years ago
5 0
Half life is the time taken by a radioactive isotope to decay by half its original mass. 
The original mass is 200 g
Time taken is 60 hours
Final mass is 25 g
Therefore;
Final mass = Original mass × (1/2)^n; where n is the number of half lives.
25 = 200 (1/2)^n
1/8 = (1/2)^n
    n = 3 
Three half lives = 60 hours
1 half lives = 20 hours
Therefore; the half life of the radioactive nucleus is 20 hours
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Answer:

               The volume is increased.

Explanation:

                     According to <em>Charles' Law</em>, " <em>at constant pressure the volume and temperature of the gas are directly proportional to each other</em>". Mathematically this law is presented as;

                                                    V₁ / T₁ = V₂ / T₂   -----(1)

In statement the data given is,

T₁  =  10 °C  =  283.15 K                    ∴  K  =  273.15 + °C

T₂  =  20 °C  =  293.15 K

So, it is clear that the temperature is being increased hence, we will find an increase in volume. Let us assume that the starting volume is 100 L, so,

V₁  =  100 L

V₂  =  Unknown

Now, we will arrange equation 1 for V₂ as,

                                                    V₂  =  V₁ × T₂ / T₁

Putting values,

                                     V₂  = 100 L × 293.15 K / 283.15 K

                                     V₂  = 103.52 L

Hence, it is proved that by increasing temperature from 10 °C to 20 °C resulted in the increase of Volume from 100 L to 103.52 L.

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b) when carbon burnt in oxygen.

C+O2----∆---> CO2.

c) when sulphur burnt in oxygen.

S+O2-----∆-----> SO2.

d) when Calcium burnt in oxygen.

2Ca+O2-----∆-----> 2CaO(black residue)

e) when Magnesium burnt in oxygen.

2Mg+O2-----∆----> 2MgO.

f) when sodium burnt in oxygen.

4Na+O2----∆-----> 2Na2O.

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Answer:

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