How many formula units are in 67.69 grams of salt?
How many molecules are in 44.99 grams of water?
To answer these questions, we need to use the concept of molar mass and Avogadro's number.
1. How many formula units are in 67.69 grams of salt?
- First, find the molar mass of the salt compound. Let's assume we are talking about common table salt, which is sodium chloride (NaCl). The molar mass of NaCl is 58.44 grams/mol (22.99 g/mol for sodium + 35.45 g/mol for chlorine).
- Next, use the molar mass to convert the given mass of salt into moles. Divide the given mass (67.69 g) by the molar mass (58.44 g/mol).
67.69 g / 58.44 g/mol = 1.16 mol (rounded to two decimal places)
- Finally, use Avogadro's number (6.022 × 10^23 formula units/mol) to calculate the number of formula units. Multiply the number of moles by Avogadro's number.
1.16 mol * 6.022 × 10^23 formula units/mol = 6.97 × 10^23 formula units (rounded to two decimal places)
Therefore, there are approximately 6.97 × 10^23 formula units in 67.69 grams of salt.
2. How many molecules are in 44.99 grams of water?
- Again, begin by finding the molar mass of the water molecule (H2O). The molar mass of water is 18.02 grams/mol (2 * 1.01 g/mol for hydrogen + 16.00 g/mol for oxygen).
- Calculate the number of moles by dividing the given mass (44.99 g) by the molar mass (18.02 g/mol).
44.99 g / 18.02 g/mol = 2.498 mol (rounded to three decimal places)
- Since one mole of water contains 6.022 × 10^23 molecules, multiply the number of moles by Avogadro's number.
2.498 mol * 6.022 × 10^23 molecules/mol = 1.505 × 10^24 molecules (rounded to three decimal places)
So, there are approximately 1.505 × 10^24 molecules in 44.99 grams of water.
To determine the number of formula units or molecules in a given amount of substance, you need to use Avogadro's number and the molar mass of the compound.
1) To find the number of formula units in 67.69 grams of salt (NaCl):
Step 1: Determine the molar mass of salt (NaCl). The molar mass of sodium (Na) is approximately 22.99 g/mol, and the molar mass of chlorine (Cl) is approximately 35.45 g/mol.
Molar mass of NaCl = (22.99 g/mol) + (35.45 g/mol) = 58.44 g/mol
Step 2: Use the molar mass and Avogadro's number (6.022 x 10^23) to convert grams to formula units.
Number of formula units = (67.69 g) / (58.44 g/mol) * (6.022 x 10^23) = 6.945 x 10^23 formula units
So, there are approximately 6.945 x 10^23 formula units in 67.69 grams of salt.
2) To determine the number of molecules in 44.99 grams of water (H2O):
Step 1: Find the molar mass of water (H2O). The molar mass of hydrogen (H) is approximately 1.01 g/mol, and the molar mass of oxygen (O) is approximately 16.00 g/mol.
Molar mass of H2O = (2 * 1.01 g/mol) + (16.00 g/mol) = 18.02 g/mol
Step 2: Use the molar mass and Avogadro's number to convert grams to molecules.
Number of molecules = (44.99 g) / (18.02 g/mol) * (6.022 x 10^23) = 1.505 x 10^24 molecules
Therefore, there are approximately 1.505 x 10^24 molecules in 44.99 grams of water.
Find the mass of Na plus the mass of Cl from the periodic table. That will give you the mass of 1 formula unit.
Water is H20 is water.
1 formula unit has a mass of approx. 18 grams
divide 44.99 by the exact value to get the number of molecules.