PHAY002; Stoichiometry

    Cards (42)

    • What does n(Cl) represent?

      Amount of chlorine atoms
    • What does n(Cl2) represent?

      Amount of chlorine molecules
    • Why do we use the term entities instead of molecules?

      Because it includes ionic substances and atoms
    • What does one mole of a substance contain?

      As many elementary entities as there are atoms in 0.012 kg of carbon-12
    • What is Avogadro's number?

      6.022×10236.022 \times 10^{23}
    • What must be specified when using the mole?
      The elementary entities involved
    • How many molecules are in 1 mol of aspirin?

      About 6.022×10236.022 \times 10^{23} C9H8O4 molecules
    • How is a mole described in terms of quantity?

      It is a number like "dozen" or "billion"
    • What is the formula to calculate the amount of substance?

      n=n =NNA \frac{N}{N_A}
    • How can the amount of substance be calculated if the mass is known?

      n=n =MMr \frac{M}{M_r}
    • What must the molar mass be in if the mass is measured in grams?

      g mol1^{-1}
    • How do you calculate the amount of aspirin in a tablet containing 300 mg?
      Convert 300 mg to grams and use n=n =MMr \frac{M}{M_r}
    • How do you calculate the mass and amount of sodium pertechnetate in a typical injection?
      Use n=n =NNA \frac{N}{N_A} and then m=m =n×Mr n \times M_r
    • How do you calculate the amount of water in sodium sulphate decahydrate?

      Use n=n =0.5 mol×10 H2O 0.5 \text{ mol} \times 10 \text{ H2O}
    • What units are used for volumes of liquids?

      mL and L
    • What is the relationship between cm3^{3} and mL?

      1 cm3^{3} is equal to 1 mL
    • What is the relationship between dm3^{3} and L?

      1000 cm3^{3} is equal to 1 dm3^{3} which is equal to 1 L
    • What is concentration?

      The quantity of substance per unit volume
    • What are typical units for concentration?

      g dm3^{-3}, mg cm3^{-3}, mol dm3^{-3}
    • What is amount concentration?

      Concentration measured in moles
    • What is the symbol for amount concentration?

      Lower case italic c
    • How is molarity defined?

      As mol dm3^{-3} or mol L1^{-1}
    • How do you calculate the molarity of a potassium iodate solution?

      Use c=c =nV \frac{n}{V} where n is the amount in mol and V is the volume in dm3^{3}
    • How do you calculate the molarity of a 0.9% m/v sodium chloride solution?

      Convert 0.9% to grams per volume and use c=c =nV \frac{n}{V}
    • What is the difference between amount of substance and concentration?

      Amount is total quantity, concentration is quantity per volume
    • How do you calculate the amount of sodium in a 0.1 m sodium sulphate solution?

      Use n=n =c×V c \times V where c is the concentration and V is the volume
    • How do you calculate the total amount of sodium chloride when mixing two solutions?

      Add the amounts calculated from each solution
    • How do you calculate the glucose concentration in a 25 mL solution?

      Use c=c =nV \frac{n}{V} where n is the amount in mol and V is the volume in dm3^{3}
    • How is percentage composition commonly expressed in medicines?

      As grams or milliliters of drug per 100 g or 100 mL of medicine
    • What is the most common way to express percentage composition?

      On a mass in mass basis
    • How do you calculate the percentage of zinc oxide in a paste?

      Use mass of zinc oxidetotal mass×100%\frac{\text{mass of zinc oxide}}{\text{total mass}} \times 100\%
    • How do you calculate the percentage mass in volume composition of sodium chloride?

      Use mass of sodium chloridevolume of solution×100%\frac{\text{mass of sodium chloride}}{\text{volume of solution}} \times 100\%
    • How do you calculate the percentage of chloroform and acetone in a mixture?

      Use volume of componenttotal volume×100%\frac{\text{volume of component}}{\text{total volume}} \times 100\%
    • Why should volume in volume percentage compositions be used for approximate work?

      Because the final volume is rarely equal to the sum of individual volumes
    • What is the distinction between a 1:5 ratio and a 1 part in 5 solution?

      A 1:5 ratio means 1 mL of the first component in 6 mL total, while 1 part in 5 means 1 mL in 5 mL total
    • What is the purpose of determining stoichiometry in chemical reactions?

      To balance the components on each side of the equations
    • What factors affect the efficiency of chemical reactions?

      Reaction conditions, choice of reactants, and properties of starting materials
    • What is the limiting reagent in a chemical reaction?

      The reagent that runs out first and limits product formation
    • How do you calculate the yield of a reaction?

      By comparing the amount of product obtained to the expected amount
    • What does a yield greater than 100% indicate?

      Possible contamination or weighing error
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