Answer the following questions. Choose the correct answer.
1
Which of the following statements correctly define Avogadro’s number?
2
If two different gas samples, Gas A (O2) and Gas B (CH4), occupy the same volume at the same temperature and pressure, what else must be true according to Avogadro's Law?
3
A non-stoichiometric oxide of iron is analyzed and found to have the formula Fe0.9501.00. Iron exists in this lattice as a mixture of Fe2+ and Fe3+ ions. What percentage of the total iron ions present are in the Fe3+ oxidation state?
4
Imagine a universe where the reference standard for the mole is redefined. Instead of Carbon-12, the mole is defined as the number of atoms in exactly 16.00 grams of Oxygen-16. If the true absolute mass of an Oxygen-16 atom is 2.657 x 10-23 grams, calculate the value of Avogadro's constant in this alternate universe and judge its impact on calculated stoichiometric coefficients in balanced equations.
5
How many grams of oxygen gas (02) are required to completely react with 12.0 grams of carbon to form carbon monoxide (CO)?
6
Devise a mathematical expression to calculate the total number of electrons present in a sample of pure water (H2O) given its mass (m) in grams, the molar mass (M), and Avogadro's number (NA).
7
A 1.50-gram sample of a metallic element M reacts completely with excess hydrochloric
acid to generate 560.0 mL of hydrogen gas (H₂) measured at STP. If the metal is known to
form M³+ ions in solution, evaluate and identify the metal.
8
A student states: "Since one mole of any ideal gas at STP occupies 22.4 liters, a 22.4-liter
flask containing NO2 gas at STP must contain exactly 3 × 6.022 × 10^23 total atoms,
regardless of whether it dimerizes into N2O4." Critique this statement.
9
A 2.00-gram sample of an organic compound containing only C, H, and O is combusted
completely in excess oxygen, yielding 4.40 grams of CO2 and 2.40 grams of H2O. A separate
mass spectrometry experiment indicates the compound's molecular mass is 60.0 g/mol.
Formulate the correct molecular formula for this compound.
10
Empirical formula differs from molecular formula because the empirical formula
always represents:
11
A mixture contains equal masses of He (Molar Mass = 4.0 g/mol) and CH4 (Molar Mass =
16.0 g/mol). What is the mole fraction of He in this mixture?
12
Two flasks, X and Y, are at the same temperature and pressure. Flask X has a volume of
1.0 L and contains Neon (Ne, 20.2 g/mol). Flask Y has a volume of 2.0 L and contains Xenon
(Xe, 131.3 g/mol). Evaluate which flask has the higher collision frequency with the walls per
unit area, assuming ideal behavior.
13
A mixture contains equal masses of He (Molar Mass = 4.0 g/mol) and CH4 (Molar Mass =
16.0 g/mol). What is the mole fraction of He in this mixture?
14
Read the question in the image.
15
Which of the following contains the greatest number of atoms?
16
Under standard temperature and pressure (STP), what is the volume occupied by one
mole of an ideal gas?
17
How many grams of oxygen gas (O2) are required to completely react with 12.0 grams of
carbon to form carbon monoxide (CO)?
18
A solid solution alloy consists of Gold (Au) and Copper (Cu). X-ray diffraction shows the
alloy has a cubic structure where Gold atoms sit at the corners of the cube and Copper
atoms sit at the centers of the faces. Evaluate the mass percentage of Gold in this specific
crystalline matrix. (Au = 197.0 g/mol Cu = 63.5 g/mol)
19
Read the question in the image.
20
Read the question in the image.
21
Read the question in the image.
22
Read the question in the image.
23
Read the question in the image.
24
What does the molar mass of a compound represent?
25
Read the question in the image.
26
An unknown gas has a density of 1.783 g/L at STP. Which of the following gases could it be?
27
Read the question in the image.
28
A 10.00-gram sample of a blend of potassium chloride (KCl, 74.55 g/mol) and sodium chloride (NaCl, 58.44 g/mol) is dissolved in water. Excess silver nitrate is added, precipitating 21.47 grams of dry silver chloride (AgCl , 143.32 g/mol). Evaluate the mass percentage of NaCl in the original mixture.
29
An unknown gas has a density of 1.783 g/L at STP. Which of the following gases could it be?
30
Consider the isotope profile of an unknown element Y. It has two naturally occurring isotopes: 63 Y and 65Y. If the average atomic mass of Y is 63.55 amu, evaluate the ratio of the number of moles of 63Y to 65 Y in a 1-mole sample of pure element Y.
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Answer: They contain the same number of molecules.
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