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Chem_mock_ans - Chem Ans 1a i Relative isotopic masses 20 Y...

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Chem Ans. 1a. i Relative isotopic masses : 20 Y = 20 21 Y = 21 ( 2 ) 22 Y = 22 ii ‘ Relative atomic mass of Y is 20.86 ‘ means that the average mass of isotopes of atom Y based on 12 C scale is 20.86. ( 2 ) Y 20.86 h Y 4 – s h -h 12 h iii. Let a% be the percentage of 22 Y, then h Y a% , 86 . 20 100 ) ( 22 ) 3 100 ( 21 ) 2 ( 20 = + - + a a a (2 ) 14 = a ( 1 ) h : Isotopic mass v 12 – carbon scale h Relative atomic mass vtX 12 – carbon scale h 1b.
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i. Ammonium sulphate can be manufactured by reacting ammonia with dilute sulphric acid. ( 1 ) x 2 NH 3 + H 2 SO 4 (NH 4 ) 2 SO 4 ( 1 ) ii. Molecular mass of urea CON 2 H 4 X = 12 + 16 + ( 14 x 2 ) + ( 1 x 4 ) = 60 g percentage by mass of N in urea (N ) = % 100 60 2 14 x x ( 2 ) = 46.7% ( 1 ) Molecular mass of ammonium sulphate (NH 4 ) 2 SO 4 4 = (14 x 4) x 2 + 32 + ( 16 x 4 ) = 132 g percentage by mass of N in ammonium sulphate (N ) = % 100 132 2 14 x x ( 2 ) = 21.2% ( 1 ) iii. Nitrogen is used to manufacture protein which is important for plant growth. ( 1 )
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( * iv. Two other factors: solubility and acidity of soil ( 2 ) h : Percentage by mass of nitrogen 4 –s percentage by mass of nitrogen 4 –s z
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