3. Given: - 99.97 g chromium - 204.47 g chlorine - 184.56 g oxygen Wanted: percent composition by mass?
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To find the percent composition by mass of each element in the compound, first you'll need to determine the total mass of all elements combined. Add up the masses: \(99.97 \, \text{g (Cr)} + 204.47 \, \text{g (Cl)} + 184.56 \, \text{g (O)} = 489.00 \, \text{g}\). Then, to find the percent composition for each element, use the formula: \(\left(\frac{\text{mass of element}}{\text{total mass}}\right) \times 100\). For chromium: \(\left(\frac{99.97}{489.00}\right) \times 100 \approx 20.4\%\); for chlorine: \(\left(\frac{204.47}{489.00}\right) \times 100 \approx 41.8\%\); and for oxygen: \(\left(\frac{184.56}{489.00}\right) \times 100 \approx 37.8\%\). Now you’ve got your percent compositions! Just remember, making sure every calculation is accurate gives you the best results. Double-check your values and calculations to avoid those pesky mistakes that can sneak in!