tema 4_ estequiometria/reacciones quimicas

estequiometria y reaciones

1. Chemical Reactions Topic 4

2. The recipe 200 g sugar 113.5 g butter 2 eggs 180 g flour 7 g baking powder 113.5 g milk In a recipe , proportions among the ingredients are fundamental and they allow us to calcula te the necessary quantities to cook/bake as much food as needed . ¿ How many eggs are needed to bake 6 muffins ? ¿ How many moles of sugar ? (sacarose: C 12 H 22 O 11 ) ¿ How many muffins can we bake with 1 kg of flour ? ¿ How many L of milk are needed ? (⍴ leche = 1,030 g·mL -1 ) ¿ How much baking powder should I use with 2,3 kg of butter ? 12 muffins

3. Summary 200 g sugar 113.5 g butter 2 eggs 12 muffins 180g /12 180 g flour 7 g baking powder 113.5 g milk Muffin Sugar BkPwd Flour Egg Milk Butter 2 /12 2 /7g

4. Stoichiometric* coefficients represent the proportions among reactants and product and allow us to calculate any quantities involved in a chemical reaction Stoichiometric coefficients * derived from the Greek words stoicheion , meaning element , and metron , meaning measure

5. Symbolic representation of a chemical reaction Chemical equations Stoichiometric coefficients Chemical formula Aggregate state Reaction arrow Reactants Products

6. B (mol) A (mol) D (mol) C (mol) Stoichiometric coefficients On the one hand… 𝛾/ ⍺ 𝛾/𝛽 ⍺/δ ⍺/𝛽 δ/ 𝛽 𝛾/δ

7. m (g) V (L) V ds (L) m ds (g) n (mol) ⍴ (g·cm -3 ) m/m (%) M (mol·L -1 ) ⍴ ds (g·cm -3 ) M molar (g·mol -1 ) c (g·L -1 ) v/v (%) General quantitative information on any one substance On the other hand…

8. Put it all together! m (g) V (L) V ds (L) m ds (g) B (mol) A (mol) D (mol) C (mol) Coefficients

9. Stoichiometry Conceptual Problems 1. How does a balanced chemical equation agree with the law of conservation of matter? 2. What is the difference between S 8 and 8S? Use this example to explain why subscripts in a formula must not be changed. 3. What factors determine whether a chemical equation is balanced? 4. What information can be obtained from a balanced chemical equation? Does a balanced chemical equation give information about the rate of a reaction? 5. If 2 mol of sodium reacts completely with 1 mol of chlorine to produce sodium chloride, does this mean that 2 g of sodium reacts completely with 1 g of chlorine to give the same product? Explain your answer. Numerical Problems 1. Balance each chemical equation. a. KI(aq) + Br 2 (l) → KBr(aq) + I 2 (s) b. MnO 2 (s) + HCl(aq) → MnCl 2 (aq) + Cl 2 (g) + H 2 O(l) c. Na 2 O(s) + H 2 O(l) → NaOH(aq) d. Cu(s) + AgNO 3 (aq) → Cu(NO 3 ) 2 (aq) + Ag(s) e. SO 2 (g) + H 2 O(l) → H 2 SO 3 (aq)

10. Answer the following questions about this reaction : 2H 2 + O 2 → 2H 2 O ¿How many hydrogen molecules are needed to react with 48 oxigen molecules? R: 96 molec H 2 If you performed the reaction and got 5 moles of water, ¿with how many moles of O 2 and H 2 would you have started with? R: 2.5 mol O 2 , 5 mol H 2 If you started with 37,5 g of O 2 , ¿how many grams of H 2 would you need? R: 4.73 g H 2 Stoichiometry Barium chloride and sodium sulfate react to produce sodium chloride and barium sulfate. If 50.00 mL of 2.55 M barium chloride is used in the reaction, how many grams of sodium sulfate are needed for the reaction to go to completion? How many grams of sodium phosphate are obtained in solution from the reaction of 75.00 mL of 2.80 M sodium the third, CO 2 . How many grams of the third product are obtained? How many grams of ammonium bromide are produced from the reaction of 50.00 mL of 2.08 M iron(II) bromide with a stoichiometric amount of ammonium sulfide? What is the second product? How many grams of the second product are produced? R: 18.105 g Na 2 SO 4 R: Grams of CO 2 : 9.24 g, Grams of Na 2 SO 4 : 22.26g R: Grams Produced: 20.37 g NH 4 Br 2 , Second Product: Iron (II) Sulfide, 9.15 g FeS