Afreshly prepared sample of curium-243 undergoes 3312 disintegrations per second. after 12.0 yr, the activity of the sample declines to 2292 disintegrations per second. the half-life of curium-243 is years.

The formation of a solid, also known as a is an indication of a chemical change. precipitate particulate particle powder

Lab reagent, hypothesis test. a reference solution used as a lab reagent is purported to have a concentration of 5 mg/dl. six samples are taken from this solution and the following concentrations are recorded: (5.32, 4.88, 5.10, 4.73, 5.15, 4.75) mg/dl. these six measurements are assumed to be an srs of all possible measurements from solution. they are also assumed to have a standard deviation of 0.2, a normal distributin, and a mean concentration equal to the true concentration of the solution. carry out a significance test to determine whether these six measurements provide reliable evidence that the true concentration of the solution is actually not 5 mg/dl.

Calculate the percent composition by mass of each element in al(oh)3. use at least three significant figures.