Chem Qs

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1.Bromine has two naturally occurring isotopes (Br-79 and Br-81) and has an average atomic mass of 79.904 amu.  The mass of Br-81 is 80.9163 amu and its natural abundance is 49.31%.  Calculate the mass and natural abundance of Br-79.


2.Fluorine-18 is a radioisotope of fluorine that is commonly used in medical imaging. It has a half-life of 109.8 minutes.

  1. Fluorine-18 undergoes positron decay. Provide the complete balanced nuclear equation that describes this reaction.
  2. What fraction of a sample of Fluorine-18 has decayed 4.0 hours after it was administered to a patient?
  3. If a patient was administered 0.500g of Fluorine-18, what mass of Fluorine-18 remains radioactive 4.0 hours after it was administered?

3.You and your research group decide to travel to Geneva, Switzerland to do an experiment at CERN at the Hadron Particle Collider.  Each of your experiments involve the following reactions, balance them and determine what you will create.

a) Curium-247 is collided with an alpha particle and ejects a proton, what element is created and balance the reaction. 

b) Nitrogen-14 is collided with Thorium-232 and ejects 2 neutrons, what element is created and balance the reaction?


4.Exposure to radiation can cause diseases, such as cancer. However, radiation is also used as a therapy to cure cancer. Explain this apparent contradiction


5.Calculate the total heat, in joules, needed to convert 32.0 g of liquid ethanol at 12.0 °C to gas at its boiling point of 78.0 °C. Ethanol has a specific heat of 2.46 J/g °C and a heat of vaporization of 841 J/g.


6.A perfect cube of gold (Au) has a mass of 0.1830 kg. Gold has a density of 19.3 g /cm3 and a specific heat of 0.0309 cal / g °

a) What is the volume of the cube?

b) The gold cube is initially at a temperature of 25.0 ° What is the final temperature of the block of gold after 124.4 cal of energy has been added to it?

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    Tags: chem
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