Question

The formula of ethanol is C2H5 – OH. What will be its molecular mass?

        I.  46 u

       II.  34 u

      III.  34 g

      IV.  46 g

7.  Number of moles present in 28g of nitrogen atoms are

        I.  1 mole

       II.  2.3 moles

      III.  0.5 mole

      IV.  2 moles

Answer 1

1). molecular mass of ethanol-

mass of c = 12
mass of H = 1
mass of 0 = 16

so, total = 46u

2).mole = weight /mass

= 28/7
= 4 moles ANSWER.

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Answer 2

Given:

1. The formula of ethanol is C2H5 – OH
2. 28g of the nitrogen atom.

To find:

1. The molecular mass.
2. The number of moles.

Solution:

1. The atomic weight of C is 12, H is 1 and oxygen is 16.

This compound has two carbon, six hydrogens and one oxygen atom.

Thus, the molecular mass of ethanol is -

12×2+6×1+16=46

The correct option is IV.

The atomic weight of a nitrogen atom is 14g.

Thus 14g N atom occupy 1 mole.

So, 28g nitrogen atom will occupy 28/14=2 moles.

Hence the correct option is IV