I understand the other problems, but i do not understand problems 11 and 12. can you explain how to do these , please

Name :` Class Period :` 8 . How many molecules of Oz are formed when 3. 09 x 10 24 molecules of KC103 are* decomposed ?` KC 10 3 - > KC1 + 02\\ 9 . How many grams of NH 3 are produced from 49 . 7 L of N2 ? N 2 + H2 - -> NH 3 10 . Identify the limiting and excess reagent if 15 L of CHA and 15 L of OZ are reacted . How many grams of water can actually be formed from this reaction ?" CHA + 202 - > CO 2 + H 20 11 . IF 56 . 8 8 HCI is reacted with excess Al ( OH )3 , determine the theoretical yield and percent yield of AICIs if you isolate 60. 3 8 of AlC/3 in a lab . AL ( OH ) 3 + 3 HC1 - > AIC/3 + 3 H 20 12 . If you start with 50.3 8 of Cr ( OH )3 and you isolate 39. 5 8 of Cris , what is the percent yield ? Cr ( OH ) 3 + 3 HI - > Cris + H 20