Question

Find the mass of one atom of uranium-235. Recall that the mass in atomic mass units is equal to the mass in grams of one mole of atoms. Avagadro's number, 6.022×1023atoms/mole, gives the number of atoms in one mole. Give your answer in kilograms to three significant figures.

Answer 1

One iron atom: The mass of one iron atom is 0.0000000000000000000000927 grams. Find the first factor by placing the decimal point after the first nonzero digit. The first factor is 9.27. The decimal point moved 23 places. Since the value of this number is less than 1, the power of 10 will be negative. So 0.0000000000000000000000927 grams can be written as 9.27 × 10-23 grams in scientific notation.

Use the same method to write the other numbers in scientific notation.

One water molecule: 0.0000000000000000000000299 grams, or 2.99 × 10-23 grams.

One silver atom: 0.000000000000000000000179 grams, or 1.79 × 10-22 grams.

One gold atom: 0.000000000000000000000318 grams, or 3.18 × 10-22 grams.

One platinum atom: 0.000000000000000000000324 grams, or 3.24 × 10-22 grams.

One uranium atom: 0.000000000000000000000395 grams, or 3.95 × 10-22 grams.

Step-by-step explanation:

Answer 2

`3.90*10^(-25)kg/atom`

Step-by-step explanation:

The molar mass of uranium-235 is 235 g/mol. So one mole of uranium-235 has a mass of 235 g. Put differently 6.022×10^23 atoms of uranium-235 have a mass of 235 g. Knowing that, how can we use that to find the mass of one atom?

mass of one atom =
`(235 g)/(1mol) *(1 mol)/(6.022*10^(23)atoms ) *(1kg)/(1000g)= 3.90*10^(-25)kg/atom`