Atomic Structure and Properties
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AP Chemistry › Atomic Structure and Properties
Which answer choice shows the correct chemical formula for barium sulfate?
Explanation
We should first remember the difference between sulfate, sulfite, and sulfide. Sulfate is , sulfite is
` and sulfide is
.
The only answer choices that could be right must have in them. We then need to see that barium usually has a charge of
, as the periodic table shows us, and so we need a charge of
to cancel that out. The answer is
.
What is the percent of carbon by mass in acetone CH3C(O)CH3?
62%
50%
75%
10%
25%
Explanation
To calculate the percent mass of a particular element within a substance I like to use a formulaic approach.
First multiply the number of moles of the atom of interest (C) by its molar mass.
3moles* 12 g/mol= 36g
Then divide by the overall molar mass of the molecule, obtain this by adding the atomic weights of each atom present in the molecule:
36g/58g= 62%
Which answer choice shows the correct chemical formula for barium sulfate?
Explanation
We should first remember the difference between sulfate, sulfite, and sulfide. Sulfate is , sulfite is
` and sulfide is
.
The only answer choices that could be right must have in them. We then need to see that barium usually has a charge of
, as the periodic table shows us, and so we need a charge of
to cancel that out. The answer is
.
What is the percent of carbon by mass in acetone CH3C(O)CH3?
62%
50%
75%
10%
25%
Explanation
To calculate the percent mass of a particular element within a substance I like to use a formulaic approach.
First multiply the number of moles of the atom of interest (C) by its molar mass.
3moles* 12 g/mol= 36g
Then divide by the overall molar mass of the molecule, obtain this by adding the atomic weights of each atom present in the molecule:
36g/58g= 62%
Which of the following isotopes has the greatest number of neutrons?
Carbon-14
Nitrogen-13
Oxygen-15
Fluorine-16
Boron-10
Explanation
Carbon-14 has 8 neutrons
Nitrogen-13 has 6 neutrons
Oxygen-15 has 7 neutrons
Fluorine-16 has 7 neutrons
Boron-10 has 5 neutrons
Which of the following isotopes has the greatest number of neutrons?
Carbon-14
Nitrogen-13
Oxygen-15
Fluorine-16
Boron-10
Explanation
Carbon-14 has 8 neutrons
Nitrogen-13 has 6 neutrons
Oxygen-15 has 7 neutrons
Fluorine-16 has 7 neutrons
Boron-10 has 5 neutrons
What is the percent composition of potassium in K2Cr2O7?
26.5%
35.4%
50%
22%
Explanation
The molecular weight of K2Cr2O7 is 2(39 g/mol) + 2(52 g/mol) + 7(16 g/mol) = 294 g/mol.
Out of this total weight, the percent composition of K is: (2(39 g/mol)/294 g) = 26.5%
What is the percent composition of potassium in K2Cr2O7?
26.5%
35.4%
50%
22%
Explanation
The molecular weight of K2Cr2O7 is 2(39 g/mol) + 2(52 g/mol) + 7(16 g/mol) = 294 g/mol.
Out of this total weight, the percent composition of K is: (2(39 g/mol)/294 g) = 26.5%
Which of the following does not have the empirical formula CH?
C6H6
Ethyne
C3H4
C100H100
Explanation
An empirical formula represents a molecule with the simplest ratio. C6H6, ethyene (C2H2) and C100H100 can all be reduced to CH, however, C3H4 cannot because it does not have C and H atoms in a 1 : 1 ratio.
What is the mass of particles of
?