Question

1. determine the percent composition of potassium dichromate, ( k_{2}cr_{2}o_{7} ). (molar mass of ( k_{2}cr_{2}o_{7}=294.2g/mol )). a. 17.5% k, 46.6% cr, 35.9% o b. 26.6% k, 35.4% cr, 38.0% o c. 36.5% k, 48.6% cr, 14.9% o d. 37.2% k, 24.7% cr, 38.1% o e. 23.2% k, 27.7% cr, 32.6% o

Explanation:

Step1: Calculate mass of each element

• Molar mass of \(K = 39.1\ g/mol\), for \(2\) \(K\) atoms: \(2\times39.1=78.2\ g/mol\)
• Molar mass of \(Cr = 52.0\ g/mol\), for \(2\) \(Cr\) atoms: \(2\times52.0 = 104\ g/mol\)
• Molar mass of \(O=16.0\ g/mol\), for \(7\) \(O\) atoms: \(7\times16.0=112\ g/mol\)

Step2: Calculate percent composition

• Percent of \(K\): \(\frac{78.2}{294.2}\times100\%\approx26.6\%\)
• Percent of \(Cr\): \(\frac{104}{294.2}\times100\%\approx35.4\%\)
• Percent of \(O\): \(\frac{112}{294.2}\times100\%\approx38.0\%\)

Answer:

B. \(26.6\%\ K, 35.4\%\ Cr, 38.0\%\ O\)