Toxicologists use the term ld50 to describe the number of grams of a substance per kilogram of body weight that is a lethal dose for 50 percent of test animals. calculate the number of arsenic(iii) oxide molecules corresponding to an ld50 value of 0.0146 for a 187−lb man, assuming that the test animals and humans have the same ld50.

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3.77 x 10²¹ arsenic(iii) oxide molecules correspond to an LD50 value of 0.0146 for a 187 lb man

Explanation: -

Weight of man = 187 lb

                         =

                          = 84.8 Kg

LD50 = number of grams of a substance that is lethal to 50% of animals per kilogram of body weight

0.0146 =

Thus

Number of grams of lethal substance = 0.0146 x 84.8

                                                                = 1.24 g

Molar mass of arsenic(iii) oxide = 197.841 g/mol

Number of moles of arsenic(iii) oxide =

                                                             =

                                                             = 0.00627 moles

Number of molecules of arsenic(iii) oxide = Number of moles x Avogadro number

                                                               = 0.00627 x 6.02 x 10²³

                                                               = 3.77 x 10²¹

some sources quote the lethal dose, for an average 170lbs opiate-naive individual is between 75 and 375 mg