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DID YOU KNOW!

DID YOU KNOW!. A recent study by Cambridge University’s Institute of Manufacturing found that 60% of the energy associated with a piece of clothing is spent in washing and drying it. Over its lifetime, a T shirt can send up to 4 kg of carbon dioxide into the air.

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DID YOU KNOW!

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  1. DID YOU KNOW! • A recent study by Cambridge University’s Institute of Manufacturing found that 60% of the energy associated with a piece of clothing is spent in washing and drying it. • Over its lifetime, a T shirt can send up to 4 kg of carbon dioxide into the air. • Rather, wash your clothes in warm water instead of hot, • Dry your clothes the natural way, by hanging them on a line instead of loading them in a dryer. • Altogether you can reduce the CO2 created by your laundry up to 90%.

  2. Limiting Reagent

  3. Reactions proceed until one of the reactants is used up and one is left in excess. • The limiting reactantis present is a smaller amount and is used up first. • The excess reactantsare present in larger amounts so are leftover after the reaction stops. • Determining the limiting reactant is important because the amount of the product formed depends on the limiting reactant.

  4. Limiting Reactant • Sandwich analogy: You want to make sandwiches for your week of lunches. Your sandwiches follow the reaction: 2 bread + 1 meat + 1 cheese 1 sandwich You have in your pantry: 10 slices of bread, 10 slices of meat, and 10 slices of cheese. What is the limiting reactant? How many sandwiches can form?

  5. 3 H2 + N2 2NH3 • What is happening in the above reaction? • 3 moles of hydrogen gas are reacting with 1 mole of nitrogen gas and producing 2 moles of ammonia. • However, every chemical reaction has alimiting reagent and an excess reagent.

  6. 3 H2 + N2 2NH3 • In this reaction, all the Hydrogen was used up, therefore it is called the limiting reagent. • The limiting reagent limits or determines the amount of product that can be formed in a reaction. • Therefore, once all the hydrogen is used up, the reaction stops. • Ex: Going to prom

  7. Example: 2Na(s) + Cl2(g) 2NaCl(s) • What will occur when 6.70mols of Na reacts with 3.20 moles of Cl2? a) What is the limiting reagent? b) How many moles of NaCl are produced? c) How much of the excess reagent remains unreacted? How do we solve questions like this???

  8. Part a:What is the limiting reagent? • 1) First check quickly if the equation is balanced. • 2) Set up a molar ratio between the information given in the question and the balanced chemical equation. • MOLAR RATIO 6.70 mols Na = x mols Cl2 2 mols Na 1 mol Cl2 x= 3.35 mols of Cl2 • You need 3.35 mols of Cl2 but they are giving you ONLY 3.20 mols of Cl2. Therefore, Cl2is the limiting reagent.

  9. Part b: How many mols of NaCl are produced? • Since you now know what the limiting reagent is (Cl2), you can use it to solve part B. • Set up a molar ratio between the limiting reagent and the product NaCl. 3.2 mols Cl2= x mols NaCl 1 mol Cl2 2 mols NaCl x= 6.40 mols of NaCl

  10. Part c: How much excess reagent remains unreacted? • The limiting reagent was found in part a to be the Cl2 . • Therefore, the Na is the excess reagent. • Set up another molar ratio between the limiting reagent and the excess reagent. 3.2 molsCl2= x mols Na 1 mol Cl2 2 mols Na x= 6.40 mols of Na 6.70 - 6.40 = 0.30 mols of Na in excess.

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