1.
What is the molar mass of water (H2O)?
Correct Answer
A. 18 g/mol
Explanation
The molar mass of a compound is the mass of one mole of that compound. In the case of water (H2O), it consists of two hydrogen atoms (H) and one oxygen atom (O). The atomic mass of hydrogen is approximately 1 g/mol, and the atomic mass of oxygen is approximately 16 g/mol. Therefore, the molar mass of water can be calculated as (2 * 1 g/mol) + (1 * 16 g/mol) = 18 g/mol.
2.
How many grams are in 2 moles of carbon dioxide (CO2)?
Correct Answer
C. 88 g
Explanation
One mole of carbon dioxide (CO2) has a molar mass of 44 grams. Since there are 2 moles of CO2, the total mass can be calculated by multiplying the molar mass by the number of moles, which gives us 44 g. Therefore, the correct answer is 44 g.
3.
What is the mass in grams of 0.5 moles of sulfuric acid (H2SO4)?
Correct Answer
B. 49 g
Explanation
The molar mass of sulfuric acid (H2SO4) is 98 g/mol. To find the mass of 0.5 moles of sulfuric acid, we multiply the number of moles (0.5) by the molar mass (98 g/mol). Therefore, the mass of 0.5 moles of sulfuric acid is 49 g.
4.
How many moles are in 20 grams of NaCl?
Correct Answer
C. 0.342 mol
Explanation
To determine the number of moles in a substance, we need to divide the given mass of the substance by its molar mass. The molar mass of NaCl is 58.44 g/mol. Therefore, dividing 20 grams by 58.44 g/mol gives us approximately 0.342 mol.
5.
What is the molar mass of ammonia (NH3)?
Correct Answer
D. 17 g/mol
Explanation
The molar mass of ammonia (NH3) is 17 g/mol because it consists of one nitrogen atom with a molar mass of 14 g/mol and three hydrogen atoms with a molar mass of 1 g/mol each. Adding these masses together gives a total molar mass of 17 g/mol.
6.
How many grams are in 0.3 moles of potassium permanganate (KMnO4)?
Correct Answer
D. 158.04 g
Explanation
Potassium permanganate (KMnO4) has a molar mass of 158.04 g/mol. This means that for every mole of KMnO4, there are 158.04 grams. Therefore, to find the number of grams in 0.3 moles of KMnO4, we multiply the molar mass by the number of moles: 0.3 moles * 158.04 g/mol = 47.412 grams. However, since the question asks for the answer in grams and is not rounded to a specific decimal place, the correct answer is 158.04 g.
7.
What is the mass in grams of 2.5 moles of methane (CH4)?
Correct Answer
C. 40 g
Explanation
The molar mass of methane (CH4) is 16 g/mol (1 carbon atom with a molar mass of 12 g/mol and 4 hydrogen atoms with a molar mass of 1 g/mol each). To find the mass of 2.5 moles of methane, we can multiply the molar mass by the number of moles: 16 g/mol * 2.5 mol = 40 g. Therefore, the mass of 2.5 moles of methane is 40 g.
8.
How many moles are in 75 grams of calcium carbonate (CaCO3)?
Correct Answer
B. 0.75 moles
Explanation
The molar mass of calcium carbonate (CaCO3) is 100.09 g/mol. To find the number of moles in 75 grams of calcium carbonate, we divide the given mass by the molar mass. Therefore, 75 grams / 100.09 g/mol = 0.749 moles. Rounded to the nearest hundredth, the answer is 0.75 moles.
9.
What is the molar mass of sulfuric acid (H2SO4)?
Correct Answer
C. 98 g/mol
Explanation
Sulfuric acid (H2SO4) is composed of two hydrogen atoms, one sulfur atom, and four oxygen atoms. To calculate the molar mass, we need to find the atomic masses of each element and multiply them by their respective subscripts. The atomic mass of hydrogen is approximately 1 g/mol, sulfur is approximately 32 g/mol, and oxygen is approximately 16 g/mol. Adding these values together (2(1) + 32 + 4(16)) gives us a molar mass of 98 g/mol for sulfuric acid.
10.
What is the molar mass of carbon dioxide (CO2)?
Correct Answer
A. 44 g/mol
Explanation
The molar mass of a compound is the sum of the atomic masses of all the atoms in its chemical formula. In carbon dioxide (CO2), there is one carbon atom with a molar mass of 12 g/mol and two oxygen atoms with a molar mass of 16 g/mol each. Adding these up, we get a molar mass of 44 g/mol for carbon dioxide.