By performing a change of units, we will see that there are 0.827 g of arsenic needed.
How to calculate the grams of arsenic?
We know that the ld50 for arsenic in humans si 13mg/kg.
Now, if there is a person of 140 lb, to find the number of grams of arsenic it would take to reach the ld50, first we need to rewrite the mass of the person in kilograms.
Remember that:
1kg = 2.2 lb
then:
1 lb = (1/2.2) kg
Then we can rewrite the mass as:
M = 140lb = 140*(1/2.2) kg = 63.64 kg.
The amount of arsenic to reach the ld50 will be:
A = (13mg/kg)*(63.64 kg) = 827.27 mg
And we want this quantity in grams, remember that:
1 mg = 1*10^(-3) g
Then we can rewrite:
A = 827.27*(1*10^(-3)) g = 0.827 g
If you want to learn more about a change of units, you can read:
https://brainly.com/question/9032119
