Duha

Cards (56)

  • Kinetic lab
    1. Demonstrate the way the breakdown of the product occurs at elevated temperature
    2. Used to forecast the rate at which activity deteriorates at temperature of storage
    3. Estimate the shelf life of the product
  • Kinetics
    Studying of reaction rate & factors affecting it
  • Reaction rate
    The velocity or the speed at which the reaction proceeds, given by ± dc/dt which gives the increase or decrease of concentration dC within a given time interval dt
  • Reaction order

    The number of atoms or molecules whose concentration determine the reaction rate, showing how the concentration of reactant affects the reaction rate
  • Factors affecting reaction rate
    • Concentration of reactant
    • Temperature
    • Catalysts
    • Presence of solvents
    • Light
    • pH
  • Half-life (t1/2)
    The time required for the drug to decompose to one half its original concentration
  • Shelf life (t90%)

    The time required for the drug to lose 10% of its original concentration, or the time required for the drug to degrade to 90% of its original concentration
  • Orders of reaction
    • Zero order: rate independent of reactant concentration
    • First order: rate proportional to first power of reactant concentration
    • Second order: rate proportional to product of two reactant concentrations
    • Third order: rate proportional to product of two reactant concentrations squared and one other reactant concentration
  • Zero order reaction
    1. Rate independent on reactant concentration, -dc/dt=k°
    2. For t50%, t50%=c°/2k
    3. For t90%, t90%=c°/10k
  • First order reaction
    1. Rate depends on 1st power of concentration of single reactant, -dc/dt=k[A]
    2. For t50%, t50%=0.693/k
    3. For t90%, t90%=0.105/k
  • For first order reactions, t50% and t90% are concentration independent
  • Arrhenius equation
    K=Ae^(-Ea/RT), where K is the specific reaction rate constant, A is the frequency factor, Ea is the activation energy, R is the molar gas constant, and T is the absolute temperature
  • The constants A and Ea in the Arrhenius equation are obtained by plotting log K vs 1/T
  • t50%
    The time it takes to reduce the concentration of a drug from 100mM to 50mM
  • t90%
    The time it takes to reduce the concentration of a drug from 100mM to 10mM
  • It takes the same amount of time to reduce the concentration of drug from 100mM to 50mM as it does from 50mM to 25mM
  • Arrhenius equation
    K = Ae^(-Ea/RT)
  • K
    Specific reaction rate constant
  • A
    Constant known as frequency factor or Arrhenius factor
  • Ea
    Energy of activation
  • R
    Molar gas constant (1.987 cal/degree.mole)
  • T
    Absolute temperature (T = 273 + °C)
  • Temperature can increase the reaction rate as expressed in the Arrhenius equation
  • Arrhenius plot
    1. Determine k at several temperatures
    2. Plot log k vs 1/T
    3. Slope = -Ea/2.303R
    4. Intercept = log A
  • Activation energy (Ea)
    The amount of energy required to put the molecules in an activated state
  • As temperature increases, more molecules are activated and the reaction rate increases
  • According to accelerated storage tests, k values for the hydrolysis of aspirin at various elevated temperatures (40, 55 & 70°C) are obtained by plotting log concentration vs time, then log k is plotted against the reciprocal of absolute temperature and the resulting line is extrapolated to room temperature
  • Arrhenius found that the speed of many reactions increases about 2 or 3 times with each 10°C rise in temperature
  • The Arrhenius equation can be used to find the reaction rate at the temperature of storage
  • The aim of the experiment is to study the effect of temperature on the hydrolysis of aspirin (1st order kinetic) in order to use it as a guide to estimate t50% and t90%
  • Materials and equipment
    • Aspirin
    • Trisodium citrate
    • NaOH
    • Phenol red indicator
    • N/20 NaOH solution
    • 250mL conical flask
    • 150mL and 50mL conical flasks
    • Pipette
    • Burette
    • Three water baths
  • Procedure
    1. Prepare a mixture of aspirin, trisodium citrate and distilled water in a 250mL conical flask
    2. Take a 10mL sample and titrate with N/20 NaOH using phenol red indicator to determine the initial aspirin concentration (X)
    3. Label 3 flasks with the experimental temperatures 40, 55, 70°C and place 80mL of the mixture in each
    4. Note the time and place the flasks in the water baths
    5. Take 10mL samples from each flask every 15 minutes for 1 hour and titrate with N/20 NaOH to determine the end point (Y1, Y2, Y3, Y4)
  • ﻞﺤﻨﻤﻟا مﻮﻳدﻮﺼﻟا ﺪﻴﺴﻛورﺪﻴﻫ
    ﺔﻴﻃوﺮﺨﻣ ةرورﺎﻗ 250ﻢﺳ
  • ﺔﻴﻃوﺮﺨﻣ ةرورﺎﻗ
    • 250ﻢﺳ
    • 150،50ﺔﺻﺎﻣ ،(ﺐﻌﻜﻣ ﻢﺳ
  • ﺔﻴﺋﺎﻣ تﺎﻣﺎﻤﺣ ﺔﺛﻼﺛ ﺔﺣﺎﺤﺳو
  • ﻂﻴﻠﺨﻟا ﺮﻴﻀﺤﺗ
    1. ﻦﻳﺮﺒﺳﻷا 4.5 مﻮﻳدﻮﺼﻟا ﻲﺛﻼﺛ تاﺮﺘﺳ 9 ﻰﻟإ ﻞﻴﻠﻗ نزو 250 ﻞﻣ
    2. ﺔﻨﻴﻌﻟا ةﺮﻳﺎﻌﻣ
    3. ﺔﻳﺎﻬﻨﻟا ﺔﻄﻘﻧ ﺪﻳﺪﺤﺗ
    4. ﺔﻴﺒﻳﺮﺠﺘﻟا ةراﺮﺤﻟا ﺔﺟرد ﺪﻳﺪﺤﺗ
    5. ﺔﻨﻴﻌﻟا ﺬﺧ
    6. ﺔﻳﺎﻬﻨﻟا ﺔﻄﻘﻧ ﺪﻳﺪﺤﺗ
  • X
    ﻦﻳﺮﺒﺳﻸﻟ ﺊﻓﺎﻜﻤﻟا مﻮﻳدﻮﺼﻟا ﺪﻴﺴﻛورﺪﻴﻫ ﻢﺠﺣ ،ﻲﺋﺎﻤﻟا ﻞﻠﺤﺘﻟا ﻞﺒﻗ
  • Y1، Y2، Y3، Y4

    ﻢﺠﺣ مﻮﻳدﻮﺼﻟا ﺪﻴﺴﻛورﺪﻴﻫ N/20 ﺔﻳﺎﻬﻨﻟا ﺔﻄﻘﻧ ﺪﻨﻋ
  • ﺔﺠﻴﺘﻨﻟا ﺔﻟوﺪﺟ

    1. ةراﺮﺤﻟا ﺔﺟرد
    2. ﺖﻗﻮﻟا
    3. ﻞﻣ NaOH
    4. c٪
    5. logc٪
  • Arrhenius ﻂﻄﺨﻣ

    1. ةراﺮﺤﻟا ﺔﺟرد
    2. 1/T
    3. K
    4. logK