relative atomic mass

Question 1

what is a relative atomic mass?

Answer 1

the average of the mass numbers of the different isotopes of an element

Question 2

what is the relative atomic mass weighted for?

Answer 2

the abundance of each isotope ( how common each isotope is)

Question 3

in chlorine, the isotope with mass number of 35 is much more common than the mass number of 37. what does this indicate about what the mass number could be?

Answer 3

the mass number will be a lot closer to 35 than 37

Question 4

how do we calculate the relative atomic mass?

(mass number of isotope 1 x percentage abundance of isotope 1) +

Answer 4

(mass number of isotope 1 x percentage abundance of isotope 1) + (mass number of isotope 2 x percentage abundance of isotope 2)

/divided by 100

Question 5

calculate the relative atomic mass of boron when the 2 isotopes are
10
B
5
20% abundance 
and 
11
B
5
80% abundance

Answer 5

10.8

the equation :
(mass number of isotope 1 x % abundance of isotope 1) + (mass number of isotope 2 x % abundance of isotope 2)

divided by 100

(10 x 20%) + (11 x 80%)
divided by 100

200 + 880 = 1080/100
10.8