1 mole of any substance has Avagadro number of molecules and it's weight is equal to its molecular weight.
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Answer 1:
Molecular weight of HNO3 = 63.01 g/mol
Therefore, 1mole of HNO3 = 63.03 g
Hence, 15.7 mole of HNO3 = 63.03 X 15.7
= 989.57 g
Thus, mass of 15.7 mole of HNO3 = 989.57 g
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Answer 2:
Molecular weight of H2O2 = 34.01 g/mol
Therefore, 1mole of H2O2 = 34.01g
Hence, 0.00104 mole of H2O2 = 34.01 X 0.00104
= 0.03537 g
Thus, mass of 0.00104 mole of H2O2 is 0.03537 g
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Answer 3:
Molecular weight of SO2 = 64.07 g/mol
Therefore, 1mole of SO2 = 64.07 g
Hence, 72.1 mmole of SO2 = 64.07 X 0.0721
= 4.619 g
Thus, mass of 72.1 mm of SO2 is 4.619 g
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Answer 4:
Molecular weight of XeF2 = 169.29 g/mol
Therefore, 1mole of XeF2 = 169.29 g
Hence, 1.23 mole of XeF2 = 169.29 X 1.23
= 208.23 g
Thus, mass of 1.23 mole of XeF2 is 208.23 g
Answer:
Explanation:
A radioactive isotope is an isotope that undergoes nuclear decay, breaking apart into a smaller nucleus and emitting radiation during the process.
The half-life of an isotope is the amount of time it takes for a certain quantity of a radioactive isotope to halve.
For a radioactive isotope, the amount of substance left after a certain time t is:
(1)
where
is the mass of the substance at time t = 0
m(t) is the mass of the substance at time t
is the half-life of the isotope
In this problem, the isotope is uranium-235, which has a half-life of
We also know that the amount of uranium left in the rock sample is 6.25% of its original value, this means that
Substituting into (1) and solving for t, we can find how much time has passed:
Answer:
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