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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: IBM on August 10, 2018, 09:06:27 PM

Title: How to get atoms of something having % of mass?
Post by: IBM on August 10, 2018, 09:06:27 PM: Two oxides of a metal contain 27.6% and 30% of oxygen respectively. If the formula of the first oxide is MO, find that of the second?
Now my problem is how to find the atoms of O from the masses of 27.6% and 30.0 %?
How to get atoms of something having % of mass? I am confused.
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 11, 2018, 03:25:09 AM: If you have, for instance 100g of oxide, what mass is M, and what mass is O? How many moles of each?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 11, 2018, 05:51:56 AM: O is 16g and M is (100-16) = 84g. 16g O = 1 mole.
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 11, 2018, 07:03:02 AM: What do the percentages you have quoted mean?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 11, 2018, 09:27:44 AM: In the first MO, if the total amount is 100g, then O is 27.6g similarly,
in the second MO, if the total amount is 100g, then O is 30g respectively
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 11, 2018, 09:50:15 AM: How many moles of O is 27.6g? In the example of MO, what is the mass of M left and how many moles of it are there?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 11, 2018, 08:43:40 PM: 1.725 mole of O is 27.6g.
in the MO, 72.4g of M left.
But my question is how to calculate the mole of M? because I don't know the molar mass of M
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 12, 2018, 03:26:44 AM: In the word MO, what is the ratio of the letters M to O?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 12, 2018, 04:58:32 AM: M:O = 1:3 or 13 : 15
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 12, 2018, 05:15:20 AM: I'm not sure where you get these figures from - care to explain a little more?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 12, 2018, 08:08:22 PM: Quote from: sjb on August 12, 2018, 03:26:44 AM
In the word MO, what is the ratio of the letters M to O?

Could you simplify your point, please?
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 13, 2018, 01:41:04 AM: If you have 1 mole of a compound MO, how many moles of M and how many moles of O do you have?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 13, 2018, 10:49:04 AM: 1 mole of M and 1 mole of O present
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 13, 2018, 01:30:26 PM: So in a sample of MO with 1.725 mole of O, how much M is there?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 14, 2018, 02:05:42 AM: in 100g MO, M = (100 - 27.6) = 72.4g
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 14, 2018, 02:15:32 AM: How many moles of M?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 14, 2018, 02:13:04 PM: 1 mole of M
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 14, 2018, 04:09:55 PM: No, if there are for example 2 moles of O in a sample of MO, how many moles of M are there?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 14, 2018, 09:49:38 PM: 2 moles of M are there
2M + 2O2 = 2MO
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 15, 2018, 01:17:28 AM: So in a sample of MO with 1.725 mole of O, how much M is there? (Ignoring the improperly balanced equation as that's not relevant at the moment)
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 15, 2018, 02:50:22 AM: 1.725 moles of M weighs 74.4g
So, 1 mole of M weighs 74.4/1.725 = 43.13g
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 15, 2018, 03:45:42 AM: Good, so in 100g of your second sample containing 30.0 % O, what is the mass of M, how many moles of M and O do you have?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 15, 2018, 02:35:15 PM: 70g of M,
1.875 moles of O and M
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 15, 2018, 03:29:40 PM: No, if the sample is 70g of M, with molecular weight 43.13g mol^-1, what is the number of moles? (Does it make sense for both numbers of moles to be increased from your first sample?)
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 16, 2018, 01:47:14 PM: 43.13g = 1 mole So, 70g = (70/43.13) = 1.62 moles
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 16, 2018, 03:49:44 PM: So what is the ratio in your second sample?
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 16, 2018, 08:32:57 PM: But how to calculate the moles' of O in the second sample?
would it be 43.13g O = 1 mole
So, 30g O =.69 mole
So. the ratio in the second sample is M:O = 1.62:.69 = 54:23
Title: Re: How to get atoms of something having % of mass?
Post by: sjb on August 17, 2018, 08:00:50 AM: You knew the mass of oxygen for sample 2 right at the start, and the atomic mass of oxygen is readily available.
Title: Re: How to get atoms of something having % of mass?
Post by: IBM on August 17, 2018, 02:33:20 PM: So, what to do now?
Title: how to calculate 'mole', 'molar mass' and 'molecular mass'?
Post by: IBM on August 25, 2018, 01:50:41 PM: Two oxides of a metal contain 27.6% and 30% of oxygen respectively. The formula is MO.
Now my questions are below:
In the case of the first formula MO:
1. If the compound is 'MO' as a product, The reactant would be 'M +0.5 O2 = MO'
So if the total amount is 100 g (MO), M + 0.5 O2 =100g. From this equation in the left side, what will be the mass of O and M (not from the MO because I am able to calculate the mass of O and M from 'MO')?
Title: Re: how to calculate 'mole', 'molar mass' and 'molecular mass'?
Post by: Borek on August 25, 2018, 02:08:24 PM: You already asked this question and received a lot of help here: www.chemicalforums.com/index.php?topic=96460.0

Topic locked.
Title: In 'MgO', If O = 1.725 mole, then how to calculate the mole of Mg?
Post by: IBM on August 25, 2018, 09:46:25 PM: Say, MgO is a compound. In this compound oxygen is 27.6%. If the total compound is 100g, If I want to calculate the moles of oxygen, that would be
16g O weigh 1 mole of O So, 27.6g O weighs 1.725 moles of O.
Now my second question is that If I want to count the mole of Mg. You would say that Mg is also 1.725 moles. but how in MgO if O = 1.725 moles, then why Mg is also 1.725 moles? I am confused here. Please explain. Please don't lock my thread in this topic. Please help me understand the concept.
Title: Re: In 'MgO', If O = 1.725 mole, then how to calculate the mole of Mg?
Post by: billnotgatez on August 25, 2018, 10:33:04 PM: topic locked
duplicate entry

@IBM
Creating multiple threads on a given topic is against the forum rules.
You were told this and decided to make this new entry which should have been in your previous post on this topic
I have banned further entries by you until we sort this out.
Title: Re: How to get atoms of something having % of mass?
Post by: billnotgatez on August 27, 2018, 10:24:32 AM: @IBM
I have combined the entries that are similar.
Making multiple entries that are alike is confusing.
Title: Re: How to get atoms of something having % of mass?
Post by: billnotgatez on August 27, 2018, 10:33:42 AM: @IBM

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