2. Find how much of the product can be produced by the reactants. Use any of the products as your guide for finding the mass of the product through stoichiometry. The one with the lesser amount of product is the limiting reagent. The one that produces more is the excess reagent. 3. Find the amount of excess reactant by subtracting the mass of the excess reagent consumed from the total mass of excess reagent given. Problem Solving Practice Problem A sample of 2g of ammonia (NH3) is added with 4g of oxygen (O2) to produce nitric oxide (NO) and water (H20). Which among the two reactants is the limiting reagent and excess reagent? 1. Balance the equation. 4 NH3 (g) + 5 02 (9) + 4 NO (9) + 6 H20 (g) 2. Use stoichiometry to calculate the amount of product each reactant can produce. Imol NHa x 4 mol NO 30g NO Excess NH3 = 2g NH3 179 NH3 4 mol NH3 X 1 mol NO 3.53g NO Reagent 1mol NH3 4 mol NO 30g NO 02 = 4g 02 329 NH3 X 39 NO Limiting 4 mol NH 3 1 mol NO Reagent 3. Find the amount of excess reactant that reacted. Amount of NHa 32g Oz NH3 = 49 02 x 1 mol 02 x 4 mol NHa x 179 NHL = 1.79 NH3 5 mol 02 1 mol NH3. that reacted with Oz 4. Find the amount of ammonia (NH3) left after the reaction. 2g NH3 (given) - 1.7g NH3 (reacted) =0.3g NH3 Remaining NH3 Practice Problem 1. Find the limiting reagent and excess reagent of respiration if there is 25g of glucose (CH120:) that reacted with 40g of Oz that produced carbon dioxide, water and ATP. ( 30]Problem Solving Practice Problem A sample of 2g of ammonia (NH3) is added with 4g of oxygen (O2) to produce nitric oxide (NO) and water (H20). Which among the two reactants is the limiting reagent and excess reagent? 1. Balance the equation. 4 NH3 (g) + 5 02 (g) 4 NO (g) + 6 H20 (9) 2. Use stoichiometry to calculate the amount of product each reactant can produce. 4 mol NO NH3 = 2g NH3 1mol NH3 30g NO Excess 179 NH3 4 mol NH3 X 1 mol NO 3.53g NO Reagent 1mol NH3 X 4 mol NO 30g NO O2 = 4g 02 329 NH3 4 mol NH3 1 mol NO 39 NO Limiting Reagent 3. Find the amount of excess reactant that reacted. Amount of NH3 NH3 = 49 02 x _ mol 02 329 02 X 4 mol NHa 179 NH 3 5 mol 02 1 mol NH. 1.79 NH 3 that reacted with Or 4. Find the amount of ammonia (NH3) left after the reaction. 2g NH3 (given) - 1.7g NH3 (reacted) = 0.3g NH3 Remaining NH3 Practice Problem 1. Find the limiting reagent and excess reagent of respiration if there is 25g of glucose (CH1206) that reacted with 40g of Oz that produced carbon dioxide. water and ATP.Problem Solving Sample Problem 1 Sample Problem 2 (relative velocity) Samantha drove 120km for 5 hrs. Barry stood in a moving 40meters What is her speed? moving sidewalk that moves 1.5m/s. Find A) how long it will take for him to Solution: reach the end of the side walk. B) How long it will take if he walked 1.7m/s to Given: d = 120km t = 5hrs reach the end in the same direction. d 120km S= -= 24km/hr 5 hrs Solution A) Given: d = 40m v = 1.5m/s d 40m 1 = 1.5m/s = 26.67s B) Given: d = 40m v = 1.5m/s Velocity of Barry = 1.7m/s 40m 1 = 1. 7m/s + 1.5m/s = 12.5s Practice Problem 1 Practice Problem 2 Find Marlyn's displacement in km if her How long will it take a passenger average velocity is 2.3m/s for 1,550 s. walking at 1.2m/s on a moving side walk with a velocity of 2.5m/s and a distance of 50m if he is moving in an opposite direction