1.) The mass of 1.21 × 10 20 atoms of phosphorous is 3.88 × 10 21 g. 2.00 mg. 30
ID: 1020410 • Letter: 1
Question
1.) The mass of 1.21 × 1020 atoms of phosphorous is
3.88 × 1021 g.
2.00 mg.
30.97 g.
6.22 mg.
2.01 × 10-4 g.
2.) Samples of the following volatile liquids are opened simultaneously at one end of a room. If you are standing at the opposite end of this room, which species would you smell first?
[Assume that your nose is equally sensitive to all these species.]
ethyl acetate (CH3COOC2H5)
camphor (C10H16O)
diethyl ether (C2H5OC2H5)
naphthalene (C10H8)
pentanethiol (C5H11SH)
3.88 × 1021 g.
2.00 mg.
30.97 g.
6.22 mg.
2.01 × 10-4 g.
Explanation / Answer
1) Atmic mass of Phosphorous is = 30.97 gm/ mole = mass of 6.023 x 1023 number of atoms
Thus, mass of 1.21 x 1020 number of atoms of phosphorous = [30.97/ 6.023 x 1023] x (1.21 x 1020)
= 0.00622 gm = 6.22 mg
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