Question

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.

Answer 1

Answer:-

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

=
`(187 lb)/(2.2 lb) x 1 kg`

= 84.8 Kg

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

0.0146 =
`(number of grams )/(Weight of man in kg)`

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 =
`(Mass)/(Molar mass)`

=
`(1.24)/(197.841)`

= 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