TEST YOURSELF 1.3 Chemistry 9th Chapter 1

TEST YOURSELF 1.3

(1)  How many amu 1 g of a substance has ?

1.66*10^-24 gram   =  1 amu

1 gram   = 1/1.66*10^-24

1 gram  = 6.0 * 10 ^-24  amu

(2)  Is atomic mass unit a SI unit of an atomic mass?

No, atomic mass unit is not a SI unit of an atomic mass.

(3)  What is the relationship between atomic number and atomic mass?

The relationship between atomic number and atomic mass is given   as following:

A = Z+n

A = Atomic mass

Z = Atomic number

n = Number of neutrons

(4)  Define relative atomic mass.

“The relative atomic mass of the atoms of an element as compared to 1/12^th the mass of an atom of carbon-12 isotope.The unit for relative atomic mass is called amu and is equal to :

1       amu = 1.66 * 10^-24 gram.

(5)  Why atomic mass of an atom I defined as relative atomic mass?

The mass of an atom of an element is too small to be determined practically. We have certain instruments which enable us to determine the ratio of the atomic masses of various elements to that of carbon-12. This ratio is called relative atomic mass of the element. Therefore, atomic mass of an atom is defined as relative atomic mass.