Moles Practice 2 (10pts)

Explanation
The molar mass of sodium chloride (NaCl) is 58.5 g/mol. To calculate the number of moles, we divide the given mass (58g) by the molar mass (58.5 g/mol). This gives us 1 mole of sodium chloride.

Explanation
The molar mass of KF (potassium fluoride) is 58.1 g/mol. To convert moles to grams, we multiply the number of moles by the molar mass. Therefore, 2.5 moles of KF would be equal to 2.5 moles x 58.1 g/mol = 145.25g. Hence, the correct answer is 145.25g, not 150g.

Explanation
One mole of any substance contains Avogadro's number of particles, which is approximately 6.022 x 10^23. To find the number of moles in a given mass of a substance, we need to divide the mass by the molar mass of that substance. The molar mass of iron (III) nitrate (Fe(NO3)3) can be calculated by adding up the atomic masses of its constituent elements. In this case, the molar mass of Fe(NO3)3 is approximately 241.86 g/mol. Therefore, 114g of Fe(NO3)3 is equal to 114/241.86 = 0.471 moles. Since the answer choices are given in increments of 0.25, the closest option is 0.500 mole.

Explanation
Calcium sulfate (CaSO4) has a molar mass of 136.14 g/mol. To find the mass of 25.0 mol of calcium sulfate, we can multiply the molar mass by the number of moles. Therefore, 25.0 mol x 136.14 g/mol = 3403.5 g. However, since the question asks for the mass in grams and the answer choices are all in grams, we can round the result to the nearest gram, which is 3180g.

Explanation
In 1.5 moles of sodium chloride (NaCl), there are 9.0 x 10^23 compounds. This is because 1 mole of any substance contains 6.02 x 10^23 particles (Avogadro's number). Therefore, 1.5 moles would contain 1.5 times that amount, which is 9.0 x 10^23 compounds.

Explanation
The correct answer is 3.0 x 10^24 molecules. One mole of any substance contains Avogadro's number (6.022 x 10^23) of particles. Since we have 5.0 moles of water, we can multiply the number of moles by Avogadro's number to find the number of molecules. Therefore, 5.0 moles x 6.022 x 10^23 molecules/mole = 3.0 x 10^24 molecules.

Explanation
The given question asks for the number of moles of hydrogen atoms when there are 1.2 x 10^24 atoms of hydrogen. To determine the number of moles, we use Avogadro's number, which states that 1 mole of a substance contains 6.022 x 10^23 particles. In this case, since we have 1.2 x 10^24 atoms of hydrogen, we can divide this number by Avogadro's number to find the number of moles. The result is 2.0 mole, indicating that there are 2 moles of hydrogen atoms.

Explanation
The molar volume of any gas at STP is given as 22.4 L/mol. Therefore, to find the volume of 4.50 moles of nitrogen gas at STP, we can multiply the number of moles by the molar volume. 4.50 moles multiplied by 22.4 L/mol gives us a volume of 100.8 L. Therefore, the correct answer is 100.8L.

Explanation
At STP (Standard Temperature and Pressure), the molar volume of all gases is 22.4 L/mol. Since the question states that the tank holds 5.00 mol of carbon dioxide, we can calculate the volume by multiplying the molar volume by the number of moles: 22.4 L/mol * 5.00 mol = 112 L. Therefore, the tank would have to be 112L in size to hold 5.00 mol of carbon dioxide at STP.