1) mass composition
N: 30.45%
O: 69.55%
-----------
100.00%
2) molar composition
Divide each element by its atomic mass
N: 30.45 / 14.00 = 2.175 mol
O: 69.55 / 16.00 = 4.346875
4) Find the smallest molar proportion
Divide both by the smaller number
N: 2.175 / 2.175 = 1
O: 4.346875 / 2.175 = 1.999 = 2
5) Empirical formula: NO2
6) mass of the empirical formula
14.00 + 2 * 16.00 = 46.00 g
7) Find the number of moles of the gas using the equation pV = nRT
=> n = pV / RT = (775/760) atm * 0.389 l / (0.0821 atm*l /K*mol * 273.15K)
=> n = 0.01769 moles
8) Find molar mass
molar mass = mass in grams / number of moles = 1.63 g / 0.01769 mol = 92.14 g / mol
9) Find how many times the mass of the empirical formula is contained in the molar mass
92.14 / 46.00 = 2.00
10) Multiply the subscripts of the empirical formula by the number found in the previous step
=> N2O4
Answer: N2O4
<span>Start with the number of grams of each element, given in the problem.Convert the mass of each element to moles using the molar mass from the periodic table.Divide each mole value by the smallest number of moles calculated.<span>Round to the nearest whole number.</span></span>
675 nanograms is equivalent to 6.75 × 10-⁴ milligrams.
<h3>How to convert nanograms to milligrams?</h3>
Nanograms is a unit of mass equal to 0.000000001 grams and has a symbol of ng.
On the other hand, milligrams is another unit of mass equal to 0.001grams and has a symbol of mg.
Nanograms and milligrams are both units of mass and can be inter-convertible as follows:
1 nanogram = 1 × 10-⁶ milligram
According to this question, 675 nanograms is equivalent to 675 × 10-⁶ milligrams.
Therefore, 675 nanograms is equivalent to 6.75 × 10-⁴ milligrams.
Learn more about milligrams at: brainly.com/question/20320382
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