Exercise 3

Exercise 3.1

SR1 SCB and SR1 SCD

Answer the questions that follow:
  1. At standard room temperature and pressure (STP), the molar volume of a gas is 22.4 dm3 while at room temperature, it is 24 dm3. Explain this phenomenon. [4]
  2. Based on this chemical equation: 2Mg + O2 à 2 MgO, explain why this equation is written as such. Your answer must include how MgO is formed and why the coefficients are written as such. [4]
  3. With reference to the following: 2Mg (s) + O2 (g) à 2 MgO (s), what information could be obtained from this chemical equation? [4]
For those who are interested to try these questions, please post your answers here. I will give my comments on your answers personally via email or written notes. These questions will test your mastery of chemistry knowledge.

7 comments:

  1. TangMarch 6, 2012 at 6:44 AM

    For question 1, i really had no idea how to answer.
    For question 2, my answer is: The MgO is formed by oxidation of magnesium. The Magnesium combined with oxygen and formed magnesium oxide(MgO).There is a number 2 in front of the MgO is to balance the coefficients.The Mg and O2 is written in front to show that they are the reatants whereas the MgO was written at the back to show that it is the product.
    For question 3, I don really know what information i can get. Like: "the Mg is a solid?" or "the O is a gas" or "the MgO is a solid?"

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    Replies
    1. KW ChanMarch 10, 2012 at 12:57 AM

      I have commented via your FB inbox.

      Delete
    2. TangMarch 10, 2012 at 7:20 AM

      i can't see anything in my inbox. Are u sure u sent to Tang Yi Chuan (tangyichuan05@yahoo.com) ?

      Delete
    3. KW ChanMarch 11, 2012 at 12:26 AM

      Your Facebook inbox..

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    4. CWMarch 25, 2012 at 7:55 AM

      1. When the temperature is 0 degree Celsius or name as standard temperature, the molar volume of a gas is 22.4 dm3. It is exactly accurate because the distance between particles of the gas are normally remain the same. While the temperature is 25 degree Celsius which is in room temperature, distance of the particles of the gas increase when particles absorb heat from the atmosphere and form more higher kinetic energy to move vastly and freely. It cause the molar volume of the gas become 24dm3 due to the systematic error occurred during the measurement.

      Delete
  2. CWMarch 25, 2012 at 8:07 AM

    2. The magnesium oxide formed when oxidation took place and magnesium was react with oxygen gas that contain in atmosphere. In the equation, the symbol of magnesium is Mg and the oxygen gas is O2 due to oxygen gas is an ion. After reaction, the result was written as 2MgO. It used to balance the equation so that it is correct and accepted. But at the equation was wrong in spite of its balance process. The number, 2 was not added to the symbol, Mg and it cause the equation unbalanced.

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  3. CWMarch 25, 2012 at 8:14 AM

    3. In the experiment, magnesium which is in solid form is reacted with oxygen which is in gas form. The reaction is named as oxidation. The the end of the experiment, magnesium oxide which is in solid form is formed.

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