The formula for copper (II) chromate is CuCrO4
- How many GRAMS of Cu2+ are present in 2.92 moles of copper (11) chromate? __________grams.
- How many MOLES of CrO42-ion are present in 1.65 grams of copper (II) chromate? __________moles.
The Correct Answer and Explanation is :
Let’s solve these problems step by step.
1. How many grams of Cu2+ are present in 2.92 moles of copper (II) chromate?
Step 1: Calculate the molar mass of copper (II) chromate, CuCrO4.
- Molar mass of Cu = 63.55 g/mol
- Molar mass of Cr = 52.00 g/mol
- Molar mass of O = 16.00 g/mol (there are four O atoms)
[ \text{Molar mass of CuCrO}_4 = 63.55 + 52.00 + (16.00 \times 4) = 63.55 + 52.00 + 64.00 = 179.55 \, \text{g/mol} ]
Step 2: Calculate the mass of Cu in one mole of CuCrO4.
Since there is one Cu atom in each molecule of CuCrO4, the mass of Cu per mole of CuCrO4 is simply the atomic mass of Cu, which is 63.55 g/mol.
Step 3: Find the mass of Cu in 2.92 moles of CuCrO4.
[ 2.92 \, \text{moles CuCrO}_4 \times 63.55 \, \text{g Cu/mol CuCrO}_4 = 185.57 \, \text{g Cu} ]
2. How many moles of CrO4^2- ion are present in 1.65 grams of copper (II) chromate?
Step 1: Use the molar mass of CuCrO4 (calculated earlier as 179.55 g/mol) to convert the mass of CuCrO4 to moles.
[ \text{Number of moles of CuCrO}_4 = \frac{1.65 \, \text{g}}{179.55 \, \text{g/mol}} = 0.00919 \, \text{moles CuCrO}_4 ]
Step 2: Calculate the moles of CrO4^2- ions.
Each molecule of CuCrO4 contains one CrO4^2- ion. Therefore, the moles of CrO4^2- ions are equal to the moles of CuCrO4.
[ 0.00919 \, \text{moles CuCrO}_4 = 0.00919 \, \text{moles CrO4}^{2-} ]
Explanation:
In copper (II) chromate, the copper cation (Cu2+) and the chromate anion (CrO4^2-) are present in a 1:1 ratio. This stoichiometry means that each mole of copper (II) chromate contains one mole of Cu2+ and one mole of CrO4^2-. When converting from moles of the compound to moles of individual ions or atoms, this 1:1 ratio simplifies calculations as each mole of the compound provides exactly one mole of each ion or atom involved.
The molar mass calculations play a crucial role in converting between grams and moles, and vice versa. It ensures accuracy in determining the exact amounts of specific ions or atoms in a given mass of compound. Such calculations are fundamental in stoichiometric computations in chemistry, which are essential for quantitative analysis in various chemical reactions and processes.
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