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Chemistry, 7/e
Raymond Chang, Williams College

Mass Relationships in Chemical Reactions

Internet Exercises

  1. Did you know that there was a day set aside to commemorate Amadeo Avogadro and his valuable constant? Find out more about this by visiting the site below and answering the following questions.
    1. On what day is National Mole Day celebrated?
      Click on the history of National Mole Day.
      Now, click on background information about Amadeo Avogadro at
    2. Why was he not recognized for his hypothesis and constant during his lifetime? When was he finally recognized?
      Now go to:
    3. How many atoms are in a 15 g sample of nitrogen?

  1. The Molecule of the Month Page displays a new and interesting molecule each month. The molecule displayed in February was urea. Go to this site and answer the following questions about this compound:
    1. Calculate the number of moles of urea (CON2H4) in 217 g.
    2. Calculate the percent composition by mass of each of the elements in urea.
    3. Calculate the number of grams of carbon in 178 g urea.
    4. Using the equation showing the formation of melamine from the dehydration of urea, calculate the number of grams of CO2 formed from the dehydration of 130 g of urea.