What is the half-life of 20 g of a radioactive sample if 5 g remain after 8 minutes?

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Answer 1 · 2016-05-31T09:23:09

#4 min.#

#m_i=m_rxx2^n#

#m_i=" is the initial mass"#

#m_r=" is the remaining mass after n periods"#

# n " is the number of periods "#

#2^n=m_i/m_r#

#2^n=20/5#

#2^n=4#

#2^n=2^2 " "=> n=2#

#n=(time)/("half-life")#

#"half-life "= (time)/n#

#"half-life" =( 8 min)/2 = 4 min#

#20 \ g -> 10 \ g -> 5 \ g#