Avogadro's number Converts particles(atoms, molecules) to/from moles x particles/mol

Transcription

1 Chem Week 9 Wednesday, March 07, 2012 Due in 2 weeks: Lecture Quiz 2 (chapters 5-6 material) in D2L MasteringChemistry Read chapter 8 Prepare for experiment 4. No more videos and prelab quizzes -complete the prelab questionsin the lab packet and bring it to lab next time. Tonight: Review/practice: mole calculations Lecture: chemical equations and balancing tips Skipping tonight: Double displacement/solubility (will learn and practice in exp 4) Lecture/demo: Reaction types Experiment 8 is tonight. We will make up exp 9 on March 28 (instead of exp 7) Chapter 6 conversions Avogadro's number Converts particles(atoms, molecules) to/from moles x particles/mol Molar mass Converts mass (g) to/from moles From periodic table - add up elements in compounds Molar mass H 2 O = g/mol Mole ratio Converts moles to moles of another substance For elements in a compound, use 1 mol of the compound per x mol element (x = subscript in formula) number of particles moles mass (g) moles another substance 90-week9 Page 1 90-week9 Page 2

2 Extra mole conversion practice How many grams C are in 2.95 mol C 3 H 8? Chapter 7: Chemical Reactions Chemical reaction: conversion of substances into different substances (by rearranging atoms) Reactants: substances present before reaction Products: substances present after reaction Chemical equation: represents a reaction on paper What is the mass in grams of 7.45 x NH 3 molecules? Reactants Products Phase labels: show the phase of reactants or products (s) : (l) : How many Na atoms are in 4.52 g sodium carbonate? (g) : (aq) : 90-week9 Page 3 90-week9 Page 4

3 Balancing chemical equations Law of conservation of mass: H 2 + O 2 H 2 O Balancing 3. If an element appears in one compound on each side, balance that element first, making the least common multiple on both sides (2b on prelab) 4. H 3 PO 3 H 3 PO 4 + PH 3 If polyatomic ions are identical on both sides, group them when counting Tips for balancing: 1. Leave elemental substances for last: CH 4 + O 2 CO 2 + H 2 O Na 2 SO 4 + Ca(NO 3 ) 2 NaNO 3 + CaSO 4 Use the chemical equations worksheet to practice writing and balancing chemical equations. Write the balanced chemical equation with phase labels for the following word description: 2. In an even/odd issue, try doubling all other coefficients Solid sodium and liquid water combine to create sodium hydoxide solution and hydrogen gas. C 4 H 10 + O 2 CO 2 + H 2 O Always make sure all coefficients are reduced to the simplest whole numbers! 90-week9 Page 5 90-week9 Page 6

4 Other reaction types 1. Combustion reaction(fire or flame are produced) carbon-containing compound + O 2 CO 2 + H 2 O Write a balanced chemical equation for the complete combustion of propane, C 3 H Other reaction types Single-displacement reaction: 1 element is replaced by another (an element + a compound another element + another compound) 2 Al(s) + Fe 2 O 3 (s) 2 Fe(l) + Al 2 O 3 (s) 2 Na(s) + 2H 2 O(l) 2 NaOH(aq) + H 2 (g) 2. Decomposition reaction: 1 reactant decomposes into 2 or more products H 2 O 2 (aq) catalystsspeed up reactions but are not consumed by the reaction -they are common in decomposition reactions H 2 O 2 (aq) 4. Synthesis reaction: 2 or more reactants form 1 product Write the synthesis reaction that silver and oxygen will undergo. 90-week9 Page 7 90-week9 Page 8

5 Review: reaction types Double displacement Combustion Decomposition Single displacement Synthesis 90-week9 Page 9