chemistry 135 chem135
Northampton Community College
Popular in chemistry of life
verified elite notetaker
Popular in Chemistry
This 3 page Class Notes was uploaded by Esraa Hagag on Tuesday October 4, 2016. The Class Notes belongs to chem135 at Northampton Community College taught by edward s fleming in Fall 2016. Since its upload, it has received 4 views. For similar materials see chemistry of life in Chemistry at Northampton Community College.
Reviews for chemistry 135
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/04/16
Chapter 7 Chemical reactions In a chemical reactions one or more pure substances are changed or transformed into new and different substances reactants products reactants and products are given by chemical symbols and formulas all chemical reactions involve release or absorption of energy formula weight: every chemical formula stands for two things the smallest particles of compound (nanoscale) an large aggregated of small particles that can be handled (macroscale) molecular compounds: 1. nanoscale formula tells us kind and number of atoms in “molecule” give us the weight or mass of a “molecule” e.g. H 2: 1 molecule of water consists of two atoms of hydrogen and one atom of oxygen Tells us the mass of one molecule of water is 2x mass of H plus mass of oxygen Mass (1 H O2molecule) = (2x) mass of H + (1x) mass of O = 2(1) + 1(16) = 18 amu Ionic compounds: Formula gives us the ratio of + to – ions in crystal Also gives formula weight e.g. CaI 2: 1 Ca for every 2 i mass of Cai 2 mass of Ca + (2x) mass of i Cai 2= 40 + 2(127) = 294 amu 2. Macroscale: Individual atoms, ions, molecules too small to be dealt with Need to have a large quantity of small particles so we can deal with them on macroscale To overcome this problem, the unit used for small particles, is the mole, mole 23 is equal to 6.02*10 units (Avogadro’s number: number in front of chemical formula is coefficient: tells us the number of moles that compound N S Al So 4 O 1 3 2 3 12 2 6 4 6 24 0.5 1.5 1 1.5 6 On macroscale a chemical formula or element symbol stand for one mole Molar mass: Chemical formula also gives the mass in grams of the substance Molar mass= sum of atomic weight of substituent elements e.g. H 2 nanoscale: 18 atomic mass unit (amu) macroscale: 18 grams (the weight of one mole of H2O molar mass of water is 18 grams/mole e.g. CaI 2 nanoscale: 294 amu macroscale: 294 g/mole (weight of 1 mole of CaI2) molar mass of CaI =2294 g/mole one mole of any substance contains Avogadro’s number of particles (atoms, ions, or molecules) but they have different molar masses (mm) molar/grams interconversion: number of moles of particular substance equals mass of substance over molar mass moles= mass/molecular mass moles=g*moles/g mass =number of moles * mm g= moles*g/mole Page 216 no. 7.4 a. number of Li atoms in 4.5 moles Li 23 24 atoms= 4.5*(6.02*10 ) atoms/mole= 2.71*10 atoms
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'