# Tricky chemistry gcse question

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#1
Hi guys!! so I've looked through the mark scheme of this question and I have the answer below but I have no idea how this is the answer or how I should work it out so can someone kindly help me and explain why this is the answer?? thank you!!

the question-

The relative formula mass (Mr) of a group 2 metal carbonate is 197.
Relative atomic masses (Ar): C=12 O=16
Calculate the relatice atomic mass (Ar) of the Group 2 metal in the metal carbonate.

Name the group 2 metal.

ANSWER- 12 + (16 x 3) = 60
197- 60 = 137
Metal- Barium or Ba
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1 year ago
#2
You don’t know the group 2 metal but you do know the carbonate. The formula for a carbonate is CO3, meaning there’s 1 carbon and 3 oxygen. Thus, you multiply the oxygen relative mass (16) with 3 and add with the 1 carbon relative mass (12) to make 60. Since you know the overall relative formula mass is 197, you take that away to get the relative mass for the group 2 metal. Then you look at your period table for the metal that has the same relative mass as 137, which is barium.
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#3
thank you so much!! ❤
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