Listed below are the amounts of mercury (in parts per million, or ppm) found in tuna sushi sampled at different stores. the sample mean is 0.836 ppm and the sample standard deviation is 0.253 ppm. use technology to construct a 90% confidence interval estimate of the mean amount of mercury in the population.

•The 90%  inverval estimate of the mean amount of mercury in the population is [0.420 ppm, 1.252 ppm].

Explanation:

1) Data:

•μ = 0.836 ppm

•σ = 0.253 ppm

•z = ?

•90% confidence interval estimate of the mean = ?

2)  Finding Zo for Pr = 90%

The symmetry of the standard normal distribution implies that, for the 90% confidence interval, 5% of the values (area) are above Zo and 5% are below = - Zo.

Using technology (statistic software) or a table of the standard normal probability, you find that for Pr ≥ 0.05 means Zo   ≥ 1.6045.

And, by symmetry, Pr ≤ 0.05 means Zo ≤ -1.6045.

3) Calculate the limits of the interval:

•Formula:  z = ( X - μ) / σ

•Upper limit:  X = zσ + μ = 1.645 (0.253 ppm) + 0.836 ppm = 1.252 ppm.

•Lower limit: X = zσ + μ = -1.645 (0.253ppm) + 0.836 =  0.420 ppm.

Then, the 90%  inverval estimate of the mean amount of mercury in the population is [0.420 ppm, 1.252 ppm] ← answer

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g

la respuesta es si te gusta hacer lo que siempre haces cuando nunca ves a alguien en el espejo porque sabes que no siempre están ahí.