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# Easy Chem Question Help Watch

1. Can I get some help working this out please?

(Molecular formula = C16H13ClN2O)

How many molecules of diazepam are in 200 mg of the drug?

Note: C = 12 g mol-1; H = 1 g mol-1; Cl = 35.5 g mol-1; O = 16 g mol-1; N = 14 g mol-1

Express your answer in index form, rounding the first box to 1 d.p.

---- x10^--
2. (Original post by Princess Kawaii)
Can I get some help working this out please?

(Molecular formula = C16H13ClN2O)

How many molecules of diazepam are in 200 mg of the drug?

Note: C = 12 g mol-1; H = 1 g mol-1; Cl = 35.5 g mol-1; O = 16 g mol-1; N = 14 g mol-1

Express your answer in index form, rounding the first box to 1 d.p.

---- x10^--
Moles of diazepam=mass/Mr
Mass you are given as 100g.
Mr can be worked out from the data
3. Be very careful here; note that the question is asking for number of molecules.

Necessary prerequisite information:

The mole ([mol.]) is a unit referring to (6.02 [...])(1023) elementary entities (molecules, ions, atoms, etc.).

Given information:

Mass (sample): 200 [mg], ≡ (200)(10-3) [g]
Diazepam formula: C16H13ClN2O

Calculations:

Molar Mass: (12)(16) + (1)(13) + (35.5) + (14)(2) + (16) = 284.5 [g][mol]-1

Moles [mol.] = (Mass [g])(Molar Mass [g][mol.]-1)-1,
Moles [mol.] = ((200)(10- 3) [g])(284.5 [g][mol.]-1)
-1 = (7.02)(10-4) [mol.]

One mole [mol.] =
(6.02 [...])(1023) molecules,
(7.02)(10-4) moles [mol.] = (7.02)(10-4)(6.02 [...])(1023) = (4.23)(1020) molecules = (4.2)(1020) molecules, to one decimal place.
4. (Original post by Наrvеу)
Be very careful here; note that the question is asking for number of molecules.

Necessary prerequisite information:

The mole ([mol.]) is a unit referring to (6.02 [...])(1023) elementary entities (molecules, ions, atoms, etc.).

Given information:

Mass (sample): 200 [mg], ≡ (200)(10-3) [g]
Diazepam formula: C16H13ClN2O

Calculations:

Molar Mass: (12)(16) + (1)(13) + (35.5) + (14)(2) + (16) = 284.5 [g][mol]-1

Moles [mol.] = (Mass [g])(Molar Mass [g][mol.]-1)-1,
Moles [mol.] = ((200)(10- 3) [g])(284.5 [g][mol.]-1)
-1 = (7.02)(10-4) [mol.]

One mole [mol.] =
(6.02 [...])(1023) molecules,
(7.02)(10-4) moles [mol.] = (7.02)(10-4)(6.02 [...])(1023) = (4.23)(1020) molecules = (4.2)(1020) molecules, to one decimal place.
Thank you!! Your explanation was great!

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Updated: March 31, 2013
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