(2) higher boiling point and lower freezing point
(3) lower boiling point and higher freezing point
(4) lower boiling point and lower freezing point
if a sample of magnesium has a mass of 60 g, how many moles of magnesium does the sample contain
Answer : The moles of magnesium will be, 2.5 moles
Explanation : Given,
Mass of magnesium = 60 g
Molar mass of magnesium = 24 g/mole
Formula used :
Now put all the given values in this formula, we get the moles of magnesium.
Therefore, the moles of magnesium will be, 2.5 moles
0.400 g
20.5 g
103 g
Answer : The correct option is, 0.200 g
Solution :
As we know that the radioactive decays follow first order kinetics.
First we have to calculate the rate constant of a samarium-146.
Formula used :
Putting value of in this formula, we get the rate constant.
Now we have to calculate the original amount of samarium-146.
The expression for rate law for first order kinetics is given by :
where,
k = rate constant =
t = time taken for decay process =
a = initial amount of the samarium-146 = 205 g
a - x = amount left after decay process = ?
Putting values in above equation, we get the value of initial amount of samarium-146.
Therefore, the amount left of the samarium-146 is, 0.200 g
Ans: 0.200 g
Given:
Half life of Sm-146 = t1/2 = 103.5 million years
Time period, t = 1.035 billion years = 1035 million years
Original mass of sample, [A]₀ = 205 g
To determine:
Amount of sample after t = 1035 million years
Explanation:
The rate of radio active decay is given as:
The years that will take or 52.5 g of a 60.0 g sample to decay to its daughter isotope is 807 years.
Half-life is the time required to decay or undergo half the process of any element.
Given the sample is 60.0 g in which 52.5 g sample has to be decay
so, 60 - 52.5 = 7.5 g
It can be seen that it goes three half life
60 >30 >15 >7.5
Now, the half life is 269
269 × 3 = 807 years.
Thus, the years taken are 807 years.
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