Question

Calculate the number of atoms in 58.7 g of
NH_{4}NO_{2}. **Ans: 4.42 x 10 ^{24}
atoms**

Answer #1

First of all, we have to calculate the moles of NH4NO2.

Given, mass of NH_{4}NO_{2} = 58.7 g

Molar Mass of NH_{4}NO_{2} = [ 14 + 4(1) + 14 +
2(16)] = 14 + 4 + 14 + 32 = 64 g/mol

Note: Molar Mass of N = 14 g/mol, Molar Mass of H = 1 g/mol, Molar Mass of O =16 g/mol

Moles of NH_{4}NO_{2} = mass of NH4NO2/Molar
Mass of NH4NO2

= (58.7 g)/(64 g/mol) = 0.9172 mol

Number of molecules (N) = Number of moles (n) x Avogadros number
(N_{A})

Number of molecules of NH_{4}NO_{2} = 0.9172 mol
x 6.022 x 10^{23} molecules/mol

= 5.5233 x 10^{23} molecules

one molecule of NH_{4}NO_{2} contains atoms =
8

5.5233 x 10^{23} molecules of
NH_{4}NO_{2} contains atoms = 5.5233 x
10^{23} x 8 = 4.419 x 10^{24} ~ **4.42 x 10 ^{24}
atoms**

(a) Calculate the number of oxygen molecules and the
number of oxygen atoms in 34.5 g of
O2.
oxygen molecules =
×
10
oxygen atoms
=
×
10
Enter your answers in scientific notation.
(b) Calculate the mass of 8.99
×
1014 SO3
molecules.
×
10
g
Enter your answer in scientific notation.

A sample of gaseous ethane (C2H6) is
found to contain 1.25 x 1024 hydrogen atoms.
a) Determine the number of moles of hydrogen atoms in the sample
of ethane.
b) Determine the number of moles of ethane molecules in the
sample.
c ) Determine the molar mass of ethane.
d) Determine the mass in grams of gaseous ethane in the
sample.

Calculate the number of atoms in a 1.74 × 103 g
sample of carbon.

A sample of C3H8 has 2.40 *
1024 atoms.
How many carbon atoms does the sample contain?
? C atoms
What is the total mass of the sample?
? g C3H8

22. Calculate the number of moles of the following atoms or
molecules: (a) 21.50 g of arsenic
(b) 66.50 g of fluorine atoms
(c) 2431 g of magnesium
(d) 15 g of chromium (III) oxide. (e) 0.0015 g of Cu(NO3)2
(f) 15.6 kg of silver chloride.
(g) 6.022x1023 molecules of N2 (h) 10 atoms of lithium.

1) A sample of C3H8 has 7.76 ×
1024 H atoms. How many carbon atoms does the sample contain?
What is the total mass of the
sample?
2) Calculate the
molar mass of each compound given
below. Keep at least one decimal place in atomic masses from the
periodic table.
a. KBr g/mol:
b.Na2s g/mol:
3) A chemist requires 0.885 mol
Na2CO3 for a reaction. How many grams does this correspond
to?

a) calculate the total number of hydrogen atoms (the
actual number, not the number of moles) in 1.78 g NH3.
b) determine the mass percent of hydrogen in 1.78 g NH3.

Calculate the number of C, H, O atoms in 5.78 g of glucose
(C6H12O6), a sugar. Enter your answers in scientific notation.

1)Calculate the number of molecules of the compound and the
number of atoms of each of the elements in 3.98 moles of SO3 . ?
molecules, ? atoms of S, ? atoms of O 2) Calculate the number of
molecules of the compound and the number of atoms of each of the
elements in 3.35 moles of P4O12. ? molecules, ?atoms of P, ? atoms
of O

Calculate the number of chlorine atoms present in 12.46 g of
CCl4. When you have the answer, take the log (base 10)
of it and enter the value with three decimal places and no
units.

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