Respuesta :
The amount of nitrogen-13 sample that remained after 40 minutes has been 8 mg.
Half-life can be defined as the time required by the substance to reduce half of its initial concentration.
The half-life of Nitrogen-13 has been 10 minutes. In 10 minutes, the sample will be reduced to
of its concentration,
The total time has been 40 minutes.
The number of half-life experienced by the sample has:
Number of half-life = {Total-time}/{Half-life}
Number of half life cycles = {40}/{10}
The number of half-life cycles = 4
The sample has been reduced to 50% in the first half-life cycle,reduced to 25% in the 2nd half-life cycle, then 12.5% in 3rd half cycle and finally 6.25% by the end of 4th half cycle.
The sample remained = 6.25% of the initial concentration.
The sample remained = (6.25/100)
×128mg
The sample remained = 8 mg
Thus from above we concluded that the amount of nitrogen-13 sample that remained after 40 minutes has been 8 mg.
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