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Solids

Solids. Solids are formed when temperatures are low enough to prevent molecules from moving around their neighbors Molecules or atoms in solids vibrate/oscillate around a fixed position All the atoms in a solid essentially move in unison. Types of Solids.

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Solids

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  1. Solids • Solids are formed when temperatures are low enough to prevent molecules from moving around their neighbors • Molecules or atoms in solids vibrate/oscillate around a fixed position • All the atoms in a solid essentially move in unison

  2. Types of Solids • Two major classifications: Crystalline and Amorphous • Crystalline Solids: All atoms, ions or molecules in the solid lie in an orderly array. Long range order exists within a crystalline solid • Amorphous Solids: The atoms, ions or molecules in an amorphous solid lie in a seemingly random arrangement. • Amorphous solids look like we took a snapshot of a liquid • Glass is an amorphous solid

  3. Crystalline Solids • Molecular Solids: Assemblies of discrete molecules held together by intermolecular forces (eg: Quartz) • Network Solids: Atoms are covalently bonded to their neighbors throughout the extent of the solid (eg: Diamonds) • Metallic Solids: Metal cations held together by a sea of electrons • Ionic Solids: Built from the mutual attraction of anions and cations

  4. Fundamentals Section L:Reaction Stoichiometry N2 (g) + 3H2 (g) --> 2NH3 (g) This tells us that 1 mole of N2 will react with 3 moles of H2 to form 2 moles of NH3 We can also relate reactants and products to each other by stoichiometric relations For the ammonia forming reaction: 1 mole of N2 is chemically equivalent to 3 moles of H2 1 mole of N2 is chemically equivalent to 2 moles of NH3 3 moles of H2 is chemically equivalent to 2 moles of NH3

  5. Using Stoichiometric Relations • We can use them to predict/calculate amounts of materials reacted or products formed • Take the fuel cell example: 2H2(g) + O2(g) --> 2H2O(l) How much water would be made from 0.25 moles of O2 reacting with H2?

  6. Looking at the chemical equation, we can see that: 1 mole of O2 is chemically equivalent to 2 moles of H2O We can set up a conversion factor based upon this relationship for use in calculations: Now we can use the stoichiometric relationship: 

  8. Calculate the mass of potassium metal needed to react with 0.450 g of hydrogen gas to produce solid potassium hydride. Step 1: Balanced chemical reaction Step 2: Take what you’re given and convert it to moles Step 3: Use the stoichiometric coefficients to convert moles of one substance to moles of another Step 4: Convert Moles to Mass

  9. Potassium superoxide, KO2, is utilized in a closed system breathing apparatus to remove carbon dioxide and water from exhaled air. The removal of water generates oxygen for breathing by the reaction: 4KO2(s) + 2H2O(l) --> 3O2(g) + 4KOH(s) Potassium hydroxide removes carbon dioxide from the apparatus by the reaction: KOH(s) +CO2(g) --> KHCO3(g) What mass of potassium superoxide generates 115g of O2? What mass of CO2 can be removed from the apparatus by 75.0 g of KO2?

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