6. Starting from 1.5 miles away, a car drives toward a speed checkpoint and then passes it. The car travels at a constant rate o
1 answer:
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Explanation:
The given data is as follows.
mass, m = 75 g
Specific heat of water = 4.18
First, we will calculate the heat required for water is as follows.
q =
=
= 8464.5 J/mol
= 8.46 kJ ......... (1)
Also, it is given that = (20 + 273) K = 293 K and specific heat of ice is 2.108 kJ/kg K.
Now, we will calculate the heat of fusion as follows.
q =
=
= -46.32 kJ ......... (2)
Now, adding both equations (1) and (2) as follows.
8.46 kJ - 46.32 kJ
= -37.86 kJ
Therefore, we can conclude that energy in the form of heat (in kJ) required to change 75.0 g of liquid water at to ice at
is -37.86 kJ.
75.17 mg of the radioactive substance will remain after 24 hours.
Answer:
Explanation:
Any radioactive substance will obey the exponential decay behavior. So according to this behavior, any radioactive substance will be decaying in terms of exponential form of disintegration constant and Time.
Disintegration constant is the rate of decay of radioactive elements. It can be measured using the half life time of the radioactive element .While half life time is the time taken by any radioactive element to decay half of its concentration. Like in this case, at first the scientist took 200 mg then after 17 hours, it got reduced to 100 g. So the half life time of this element is 17 hours.
Then Disintegration constant = 0.6932/Half Life time
Disintegration constant = 0.6932/17=0.041
Then as per the law of disintegration constant:
Here N is the amount of radioactive element remaining at time t and is the initial amount of sample, x is the disintegration constant.
So here, = 200 mg, x = 0.041 and t = 24 hrs.
N = 200 × =75.17 mg.
So 75.17 mg of the radioactive substance will remain after 24 hours.