Answer: (a) There are 0.428 moles present in 12 g of 
molecule.
(b) There are 2 moles present in 
particles of oxygen.
Explanation:
(a). The mass of nitrogen molecule is given as 12 g.
As the molar mass of is 28 g/mol so its number of moles are calculated as follows.
So, there are 0.428 moles present in 12 g of molecule.
(b). According to the mole concept, 1 mole of every substance contains 
atoms.
Therefore, moles present in particles are calculated as follows.
So, there are 2 moles present in particles of oxygen.
C. 2Fe2O3 would be the correct answer!
A) Ca(OH)2 + CO2 —> CaCO3 + H2O
B) when Ca(OH)2 is reacted with CO2, the CaCO3 produced is a precipitate which turns the solution milky
Ultrasound is sound or vibrations, having an ultrasonic frequency, particularly as used in medical imaging. Ultrasound is more commonly used in medical terminology than in industry. Infrasound is sound waves with frequencies below the lower limit of human audibility.
1) An example of a compound machine could be a pair of Scissors. Their are two different simple machines in the Scissors which make up the compound machine. Both of them being a Lever, and a Fulcrum.
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