Need a bit of homework help about % mass of elements

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To calculate the percentage by mass of elements in compounds, use the formula: (mass of element in compound / mass of total compound) * 100%. For MgBr2, consider the contribution of two bromide ions. In Ca(NO3)2, account for the nitrogen and oxygen from the nitrate groups. For NH4NO3, include the masses of both nitrogen sources. Understanding the molecular composition is crucial for accurate calculations.
rpatel
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Calculate the percentage by mass of the elements shown in the following compounds

A) Br in MgBr2

b) O in Ca(NO3)2

c) N in NH4NO3


any help is appreichated

thanks

regards
 
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the percent mass will be equal to [mass of element in compound]/[mass of total compound]*100%. The only thing to watch out for is when a compound has a few atoms of the same element in it. [ie: for the first one you have 2 bromide ions so the answer would be 2*molecular mass of bromide / mass of magnesium (II) bromide * 100%]
 
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thank you. :smile:
 
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