The calculation provided is correct for finding the relative atomic mass of M in M2CO3. In this compound, there are two oxygen atoms with a total atomic mass of 16 x 2 = 32, one carbon atom with an atomic mass of 12, and two atoms of M with a total atomic mass of 2x.
Adding up all the atomic masses gives us:
690 = 2(x) + 32 + 12
690 = 2x + 44
646 = 2x
x = 323
Therefore, the relative atomic mass of M in M2CO3 is indeed 323.
clarify there are three 0xygen atoms M 2 C (03) (16x3)
Apologies for the confusion. In the compound M2CO3, there are three oxygen atoms, not two. Therefore, the total atomic mass of oxygen in the compound would be 16 x 3 = 48. The calculation to find the relative atomic mass of M would be as follows:
690 = 2(x) + 48 + 12
690 = 2x + 60
630 = 2x
x = 315
Therefore, the correct relative atomic mass of M in M2CO3 is 315. Thank you for pointing out the error.