The amount of nitrogen-13 sample that remained after 20 minutes has been 32mg.
Half-life can be described 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 half of its concentration,
The total time has been 20 minutes.
The number of half-life experienced by the sample has:
Number of half-life = [tex]\rm \dfrac{Total-time}{Half-life}[/tex]
Number of half life cycles = [tex]\rm \dfrac{20}{10}[/tex]
The number of half-life cycles = 2
The sample has been reduced to 50% in the first half-life cycle and reduced to 25% by the end of 2nd half-life cycle.
The sample remained = 25% of the initial concentration.
The sample remained = [tex]\rm \dfrac{25}{100}\;\times\;128 mg[/tex]
The sample remained = 32 mg
The amount of nitrogen-13 sample that remained after 20 minutes has been 32mg.
For more information about the half-life, refer to the link:
https://brainly.com/question/24710827
