Chemistry-Quantitative chem

avatar
Created by
cookies

Cards (24)

  • percentage mass=Ar x number of atoms of that element/Mr of compound x 100
  • Mole is the amount of an substance
  • Avogadro constant is 6.02x10^23
  • One mole of atoms or molecules of any substance will have mass in grams equal to relative formula mass
  • Carbon has an Ar of 12 so one mole of carbon is exactly 12 grams
  • Number of moles = mass in grams(element or compound)/Mr(of element or compound)
  • During a chemical reaction no atoms are destroyed or created
  • if mass increases one of the reactants may be a gas found in air and all the products are solids, liquids or aqueous.
  • metal + oxygen = metal oxide
  • before the reaction the gas is floating in the air so its mass is not accounted for in the reaction. But when the reaction happens and the gas reacts to form part of the product. Therefore total mass increases.
  • if mass decreases it is probably because one of the products is a gas and reactants are solid, liquid or aqueous.
  • if vessel isn't closed during reaction then gas can escape from the vessel as its formed. Since its no longer contained its mass cant be accounted for so total mass of reaction decreases.
  • the reactant that is used up is called the limiting reactant
  • when other reactants are in excess it is to ensure that the other reactant is used up.
  • the amount of product formed is directly proportional to the amount of limiting reacant.
  • you can calculate the mass of a product formed in a reaction by using the mass of the limiting reactant and the balanced symbol equation.
  • one mole of any gas occupies 24dm^3 at 20 degrees Celsius.
  • At the same temperature and pressure, equal numbers of moles of any gas will occupy the same volume.
  • volume of gas in dm^3= Mass of gas in G/ Mr of gas x 24
  • The amount of a substance in a certain volume of a solution is called it's concentration
  • The more solute there is in a given volume, the more concentrated the solution
  • concentrationg/dm3=concentration g/dm^3=massofsolute(g)/volumeofsolvent(dm3)mass of solute(g)/volume of solvent(dm^3)
  • Concentration(mol/dm^3)=number of moles of solute(mol)/volume of solvent(dm^3)
  • cm^3-dm^3= divide 1000 other way times by 1000 same for dm^3-m^3= divide by 1000