Use Avogadros number and molar amounts 005 mol NH 4 2 SO 4 602 x 10 23

# Use avogadros number and molar amounts 005 mol nh 4 2

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Use Avogadro’s number and molar amounts 0.05 mol (NH 4 ) 2 SO 4 6.02 x 10 23 molecules CaSO 4 1 mol CaSO 4 x 3 mol CaSO 4 3 mol (NH 4 ) 2 SO 4 x = 3.01 x 10 22 molecules CaSO 4 20 In Summary Using only balanced reaction equations , the periodic table and Avogadro’s number one can find: - Formula mass (molar mass) of any reactant/product - Number of moles of any reactant/product (used/produced) - Mass of any reactant/product used/produced - Number of atoms of any reactant/product (used/produced) - The limiting reagent and the excess reagent(s) An immense amount of information comes from something so simple as a written reaction equation!! 21 Solutions A solution is a homogeneous mixture of some solute and some solvent Homogeneous – cannot be separated by filtration, single phase Usually we deal with aqueous solutions The component of the solution that changes state is called the solute Generally, “what gets dissolved” The component that keeps its state is called the solvent Generally, “what does the dissolving” If both components start in the same state, the major component is always the solvent 22 Describing Solutions Because solutions are mixtures, the composition can vary from one sample to another pure solutions have constant composition water samples from different bodies of water have different amounts of salt An accurate description will tell you how much of each component is present Usually described as a concentration Often a percentage” or “parts” 23 Solution Concentration Solutions are simplistically described as dilute or concentrated Dilute solutions have a small amount of solute compared to solvent Concentrated solutions have a large amount of solute compared to solvent Not necessarily intuitive 24 Concentrations—Quantitative Descriptions of Solutions A more precise method for describing a solution is to quantify the amount of solute in a given amount of solution Concentration is the amount of solute in a given amount of solution Occasionally based on solvent amount Not very useful or common 25 Molarity Most common unit of concentration is molarity (M) Defined as moles of solute per 1 liter of solution Used because it describes, in a way, how many molecules of solute are in each liter of solution Moles solute L solution M = * Molarity can be used as a conversion factor between moles and L * #### You've reached the end of your free preview.

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