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Homework Set #5 (Chapter 1-3)
(You will need to use a separate sheet of paper for each problem. Please show all work especially units & sig figs)
1. Washing soda, a compound used in laundry, is a hydrate whose formula can be written as Na2CO3xH2O where x is the number of water per mole of Na2CO3. When a 2.558g sample of washing soda is heated at 125 degC, all of the water of hydration is lost, leaving 0.948g of the Na2CO3. What is the value of x?
2. A student took an unknown sample mass of a compound that consists of Ti and Cl and put it into some water. The Ti formed TiO2, which was removed, dried and found to weigh 0.777g. AgNO3 was then added to the solution until all of the Cl1- ions were converted to 5.575g of AgCl. Determine the empirical formula of the compound of Ti and Cl.
3. An impure sample of zinc is treated with excess of sulfuric acid to form zinc sulfate and hydrogen gas. Write the equation for the reaction. If 0.0764g of H2 is obtained from 3.86g of the sample, calculate the percent purity of the sample. What assumption must you make?
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