Question
https Pmail.google.com scs/mail-static juk-gmail.maim.em.BN.. Na Prelaboratory Problems- Experiment 2- Empirical Formulas ase Lab Section 21 1.: 5.0 g of aluminum and 5.0 g of oxygsn are reaced and yield the exgected rouc. Write a balanced equation for the reaction. a. b. Wh ich one of the two reagents was used in excess and how much of it remains after the reaction is complete (the other reagent is called the limiting reagent), 2. 2.2 0 grams of chromium reacts with excess oxygen to give 3.22 grams of a chromium oxide. What is the name and formula of the chromium oxide? Write a balanced equation for the reaction 3. Complete and balance the following equations: 4. What is the percent by mass of water in: a." BaCl, 2H,O b. Co(CH,O) 4H,o Determine the empirical formula and the molecular formula of a compound (Freon 11) that 5 consists of 8.74% C, 77.43% CI, 13.83% F and has a molecular mass of 137 gmol. at © 2015 Cengige Leaning All Rights Reserved. May na te iamet opted ordiglied plasi pthly reek
Explanation / Answer
4Al + 3O2 Give 2Al2O3
Molar mass of Al = 26.98 g/mol
Molar mass of O2 = 32 g/mol
number of moles of Al = mass / molar mass = 5/26.98 = 0.185
Number of moles of O2 = 5/32 = 0.15625
As per balanced chemical equation, one mole Al reacts with 3/4 moles oxygen. ie 0.13875 moles of O2 for 0.185 moles Al
Current number of moles of oxygen = 0.15625-0.13872 = 0.0175 moles
mass of excess oxygen = 0.56 g
oxygen is the excess reagent.
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