Asked in ETEA MDCAT 2005 2005Moderate

The number of oxygen in 0.5 mole of AI2 (CO3)3 is:

Correct answer: C. 2.7 x 10^24

  • A. 4.5 x 10^23
  • B. 3.6 x 10^24
  • C. 2.7 x 10^24
  • D. 9.0 x 10^23

Explanation

In one molecule of aluminum carbonate, there are 3 molecules of carbonate ions, which have 3 oxygen atoms each so there are 9 atoms of oxygen in 1 molecule of aluminum carbonate. Therefore in 0.5 moles of aluminum carbonate, there are 0.5NA particles of aluminum carbonate which means there are 9 * 0.5NA = 4.5 NA particles of oxygen. 1 NA = 6.02 x 1023 so 4.5 NA = 4.5 x 6.02 x 1023 = 27 x 1023 = 2.7 x 1024 atoms of oxygen. Hence, C is the correct answer.

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