Question

1. how many molecules of nitrogen monoxide are in a 22.6 gram sample?

a) 4.51×10²³
b) 7.33×10²³
c) 5.86×10²³
d) 4.06×10²³
e) none of the above

1. one mole of ammonium nitrite contains

a) 4 moles of hydrogen atoms
b) all of a, b, and c
c) none of a, b, and c
d) 2 moles of nitrogen atoms
e) 2 moles of oxygen atoms

1. how many moles of carbon are in 3.5 moles of calcium carbonate?

a) 10.5
b) 7
c) 3.5
d) 100.09
e) none of the above

1. if a sample of carbon dioxide contains 3.8 moles of oxygen atoms, how many moles of carbon dioxide are in the sample?

a) 7.6
b) 11.4
c) 1.9
d) 3.8
e) none of the above

1. a 42.7 gram sample of potassium nitrate contains how many grams of potassium?

a) 8.54
b) 39.1
c) 21.4
d) 16.5
e) none of the above

1. a 500. gram iron ore sample was determined to contain 242 grams of iron. what is the mass percent of iron in the ore?

a) 48.4
b) 93.7
c) 51.6
d) 32.6
e) none of the above

1. the empirical formula of a compound

a) is the same as the molecular formula.
b) is none of the above
c) describes the composition of the molecule.
d) indicates the structure of the molecule.
e) indicates the simplest ratio of atoms in the compound

Explanation:

Step1: Calculate moles of nitrogen monoxide in 22.6 - gram sample

The molar mass of nitrogen monoxide (NO) is $M = 14.01+16.00=30.01\ g/mol$. The number of moles $n=\frac{m}{M}$, where $m = 22.6\ g$. So $n=\frac{22.6\ g}{30.01\ g/mol}\approx0.753\ mol$.

Step2: Calculate number of molecules

Using Avogadro's number $N_A = 6.022\times 10^{23}\ molecules/mol$, the number of molecules $N=n\times N_A$. So $N = 0.753\ mol\times6.022\times 10^{23}\ molecules/mol\approx4.54\times 10^{23}$ molecules.

For question 23:
The formula of ammonium nitrite is $(NH_4)_2NO_2$. One - mole of $(NH_4)_2NO_2$ contains 8 moles of hydrogen atoms, 2 moles of nitrogen atoms and 2 moles of oxygen atoms.

For question 24:
The formula of calcium carbonate is $CaCO_3$. In one mole of $CaCO_3$, there is 1 mole of carbon. So in 3.5 moles of $CaCO_3$, the number of moles of carbon is 3.5 moles.

For question 25:
The formula of carbon dioxide is $CO_2$. In one mole of $CO_2$, there are 2 moles of oxygen atoms. If there are 3.8 moles of oxygen atoms, the number of moles of $CO_2$ is $n=\frac{3.8\ mol}{2}=1.9\ mol$.

Answer:

E. none of the above