What is the percent by mass of sodium in na2so4?

= 32.39 %

Explanation:

The relative atomic mass of sodium is 23, sulphur 32 while oxygen as a relative atomic mass of 16.

I mole of Na₂SO₄ has a relative mass of 2(23) + 32 + 4(16) = 142 grams

Of the value 142, the contribution of sodium is 2×23 =46

Thus the % composition is calculated:

46/142×100%= 32.39%  

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally