Answer:
Calculate the mass percent of a potassium nitrate solution when 15.0 g KNO3 is dissolved in 250 g
of water.
2. Calculate the mass percent of a sodium nitrate solution when 150.0 g NaNO3 is dissolved in 500 mL
of water. Hint: 1 mL water = 1 g water
3. Calculate the weight of table salt needed to make 670 grams of a 4.00% solution.
4. How many grams of solute are in 2,200 grams of a 7.00% solution?
5. How many grams of sodium chloride are needed to prepare 6,000 grams of a 20% solution?
Mass Percent = Grams of Solute
Grams of Solution X 100%
100%
Grams of Solute = Grams of Solution X Mass Percent
= 26.8 grams NaCl
= 670 grams X 4.00%
100%
100%
Grams of Solute = Grams of Solution X Mass Percent
= 154 grams solute
= 2,200 grams X 7.00%
100%
100%
Grams of Solute = Grams of Solution X Mass Percent
= 1,200 grams NaCl
= 6,000 grams X 20.0%
100%
Explanation:
Approximately .
The relative atomic weight of an element is a weighted average of the atomic mass for all its isotopes. It accounts for the atomic mass for each isotope, as well the relative abundance of each.
The question provides no detailed data on the relative mass for each isotope atom. Each nucleon- proton or neutron- has a mass of approximately . The mass number of an atom gives the total number of nucleons it contains. The mass number can, therefore, serve as a numerical estimator for the relative atomic mass of an isotope. That is:
- Copper-63 has mass number 63 and a relative atomic mass of approximately ;
- Copper-65 has mass number 65 and a relative atomic mass of approximately
Copper-63 has an abundance of 69.17% relative to all copper atoms. Similarly, copper-65 has a relative abundance of 30.83%. Therefore, one would expect to find 6,917 copper-63 atoms and 3,083 copper-65 atoms in a sample of 10,000 copper atoms. Similarly, 10,000 <em>moles</em> or 10,000 × (6.02 × 10²³) copper atoms would contain 6,917 <em>moles</em> of copper-63 atoms and 3,083 <em>moles</em> of copper-65 atoms.
10,000 moles of copper atoms would have a mass of approximately
.
Each mole of copper atoms would thus have a mass of approximately
.
Combining the two previous steps would give:
,
which essentially multiplies the relative atomic mass by their relative abundance, and takes the sum of the products.
The relative atomic mass of an element is measured in grams per mole. One mole of copper atoms have a mass of 63.62 grams. Copper thus has a relative atomic mass of .
Hello friend, the answer would be 1609.34. Hope it helps. :) BTW, I've also double checked for you. :)