Properties of Matter Are mass, volume and density intensive or extensive properties? Are taste and smell intensive or extensive properties? Problem Set Reacting Quantities: Masses

Chemical Stoichiometry Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

6/27/2015 Chemical Equations  Stoichiometry (atom balance)  Charge (charge balance)  Format Phase annotation (s, l, g, aq) Arrow notations  Reading assignment Zumdahl: Chapter ,

6/27/2015 Annotated ( g, l, s, aq ) Equations  The phase of a reactant or product is often important. gas liquid solid aqueous solution Write an annotated equation for the decomposition of a 3% solution of hydrogen peroxide to give water and oxygen.

6/27/2015 Things to Think About when Writing a Chemical Equation.  What is the formula of the reactant & product?  What is the phase of the reactant & product?  Does it dissolve? What would you observe? How could you predict it? Write an equation for what occurs when solid sodium hydrogen carbonate is mixed with water.

6/27/2015 Solid Sodium Hydrogen Carbonate is Mixed with Water NaHCO 3 (s)NaHCO 3 (aq) NaHCO 3 (s)Na + (aq) + HCO 3 – (aq) How could you tell? Does it ionize?

6/27/2015 Sodium Hydrogen Carbonate Why is it called sodium bicarbonate? - C OO O - carbonate ion C OO O - H bicarbonate ion C OO O H H carbonic acid

6/27/2015 Nomenclature Give two acceptable names for each of these ions. HSO 4 – HSO 3 – HS –

 Let  be oxygen  be carbon  be hydrogen  be sodium  be chlorine  Rewrite the equation in terms of graphics How does your chemical equation demonstrate Dalton’s atomic theory? HCl( g ) + NaHCO 3 ( aq )NaCl( aq ) + CO 2 ( g ) + H 2 O( l )

Atomic Theory John Dalton (1809) In a chemical reaction, the way the atoms are bound together changes, but the atoms don’t change.              

 Each elemental substance cannot be divided indefinitely, but is composed of fundamental subunits called atoms.  Atoms of different elements have different properties mass, size, reactivity, etc.              

 In chemical reactions, atoms are never interconverted, created or destroyed.  Each pure compound contains different elements which occur in a specific ratio with respect to one another.  Chemical changes involve the rearrangement of atoms.              

19th Century Chemistry 3 grams of carbon 4 grams of oxygen 400 grams 300 grams Analyzed reactions using weights and volumes

Amadeo Avogadro (1811)  In a fixed volume, at a given temperature and pressure, every gas contains the same number of particles (molecules). Avogadro never heard of the term mole, or Avogadro’s Number! Theory was not accepted for 50 years. hydrogenoxygen

Atoms are Small  Generally measured in atomic mass units (amu) or daltons  Carbon-12 (6 protons and 6 neutrons) has a mass of exactly amu  The conversion factor from an atomic quantity (amu) to a measurable quantity (gram) is the mole.

A Mole is Big  One mole equals x units of anything.  x amu = mole of amu = gram

Limestone  Limestone is a naturally occurring material consisting principally of calcium carbonate.  Upon heating (roasting) at >1000  C, it decomposes into calcium oxide (lime) and carbon dioxide. You are the chief engineer. How could you determine when this roasting process is completed?

Limestone  If you began with grams of limestone, and the limestone was heated, what would be the percentage converted when the mass of solid is 900. grams? what would be the mass of solid when it is 95% converted?

6/27/2015 Problem Set Reacting Quantities: Masses

Hydrogen Peroxide Decomposition 30% H2O2H2O2 decomposes H2OH2O water from decomposition and original water 2 H 2 O 2 (aq)  2 H 2 O (l) + O 2 (g) 70% water

Team Peroxide  With your team "diagram" your approach to solve the following problem.

u Concentrated hydrogen peroxide contains 30% hydrogen peroxide by weight and the balance water. The density of 30% hydrogen peroxide is gmL -1. u Hydrogen peroxide decomposes upon standing, over a period of several months, to form water and oxygen. u Assume an empty 500 mL plastic bottle used to hold hydrogen peroxide has a mass of grams. 30% H2O2H2O2 decomposes H2OH2O

u What would be the difference in mass and the percentage difference in mass between 500 mL of fresh 30% hydrogen peroxide in the 500 mL bottle and a bottle of hydrogen peroxide which is decomposed? u Assume any oxygen gas formed escapes. u The density of water at 25.0 °C is gcm -3. u The density of pure hydrogen peroxide is gcm % H2O2H2O2 decomposes H2OH2O

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