Give the correct number of significant figures in 1.900.0 kg*

Use examples from the article to explain one positive and one negative effect that chemistry has had on society.

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

What is the mass of 0.46 mol of mgcl2