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(a) What is the mass of nitrogen present in the sample of sodium nitrate (NaNO3) which contains 100g of sodium?
(b) What is the mass of water of crystallization present in the sample of sodium carbonate10water (Ma2CO3·10H2O) which contains 4.6g of sodium?
(c) A metal oxide MO contains 79.87% by mass of the metal M. Find the relative atomic mass of M.
(d) 26.88g of a metal chloride MCl contains 5.68 g of chlorine. Find the relative atomic mass of the metal M.
 one year ago
 one year ago
(a) What is the mass of nitrogen present in the sample of sodium nitrate (NaNO3) which contains 100g of sodium? (b) What is the mass of water of crystallization present in the sample of sodium carbonate10water (Ma2CO3·10H2O) which contains 4.6g of sodium? (c) A metal oxide MO contains 79.87% by mass of the metal M. Find the relative atomic mass of M. (d) 26.88g of a metal chloride MCl contains 5.68 g of chlorine. Find the relative atomic mass of the metal M.
 one year ago
 one year ago

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gerryliyanaBest ResponseYou've already chosen the best response.0
(Ar Nitrogen/Mr NaNo3) x mass of NaNO3
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
Ar stands for what?
 one year ago

gerryliyanaBest ResponseYou've already chosen the best response.0
mass of relative atom
 one year ago

gerryliyanaBest ResponseYou've already chosen the best response.0
Mr is "mass of relative molecule"
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
no need to times 100g?
 one year ago

gerryliyanaBest ResponseYou've already chosen the best response.0
do you have a periodic table?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
\[\large m \text { N}=100g \text { Na} \times \frac{ 14g \text{ N} }{ 23g \text { Na} } \approx 61g \text { N}\]
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
Na=23.0g N=14.0g O=16.0g
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
why 23g Na?? not NaNO3?
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
but my idea is this... dw:1354705910345:dw
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
our interest is in the element Na and N in the compound. the ratio of these elements is 1:1
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
uhhh...what do you mean?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
the compound contains 100g of Na. it did not say the compound NaNO3 weighs 100g.
 one year ago

gerryliyanaBest ResponseYou've already chosen the best response.0
yes sodium is Na.., so 100 is mass of Na
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
@sirm3d so it depends on the question asking about the mass of something which contains how many grams of that thing, right? @gerryliyana that hundred of sodium represents what? the mass or the weight?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
yes. be careful of the question. if the 100g is the mass of the compound NaNO3, then we need to compute the mass on Na in the compound.
 one year ago

gerryliyanaBest ResponseYou've already chosen the best response.0
represent mass of Na
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
@sirm3d okay, how about part b? @gerryliyana thanks, I got it :) part b please
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
same thing. The mass of Na in the compound, sodium carbonate decahydrate, is 23g. we compute the total mass of water molecules in the compound
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
mass of 10 moles of water is 10 x 18g = 180 g
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
we convert 4.6 g Na to g H2O by the mass ratio in the compound (180 g H2O / 23 g Na)
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
but there are two Na atom.... Na2Co3
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
sorry for typing mistakes, it should be Na2CO3 10H2O
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
sorry, missed that two Na. Mass of Na in compound is 46 g. use the mass ratio 180g H2O / 46g Na
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
dw:1354706692310:dw
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
thanks. How about part c?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
assume 100g mass of compound MO. Mass of M in 100g compound is 79.87 g, mass of O in 100g compound is 20.13 g.
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
so what is the formula about finding relative atomic mass of M?
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
there is no answer on my textbook. I cannot ask my teacher since I will have Chemistry examination tonight.
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
it is the mass of M relative to the mass of O
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
there are 1 atom of M, right?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
yes, 1:1 ratio. so the mass of the oxygen in MO is 16g. the mass of M relative to 16g O present in the compound is the relative mass of M
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
mass of M=79.87g and the relative atomic mass is ...?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
if there is 1 mol of MO, the mass of M is 63.5 g. if there are 2 mol of MO, the mass of M is 127g. relative mass means mass in ONE mol of the compound.
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
how can you get the answer?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
we assumed that IF there are 100g of MO, clearly 79.77% of that mass belongs to M. you would arrive at the same result if you assume that the starting mass of MO is 20g. In this 20g MO, the mass of M is 79.87% of 20g while 20.13% of 20g is the mass of O.
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
you cannot give the actual mass of M in the compound MO if you do not have the actual mass of MO.
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
i'll give an analogy just to be clear with the "relative" mass. Suppose you got 90% of the questions in your exam, can you tell me how many correct answers you got?
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
if there were 100 questions in my exam, I got 90 questions correct. I know why you assume 100 g be the mass of the compound MO and the ratio is 1:1 total mass =100 g mass of M=79.87 g mass of O=20.13 g relative atomic mass of O=16.0 g But I am confusing how to get the relative atomic mass of M...... I still cannot get you idea about M...
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
we convert the relative atomic mass of O = 16.0g to relative atomic mass of M using the available masses of 79.87g M and 20.13g O.
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
16.0g O x 79.87g M / 20.13g O = 63.5g M
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
the relative atomic mass of O is known and ask for the relative atomic mass of M, we need to make the mass of O be the denominator and mass of M be the numerator. If the relative atomic mass of M is known and ask for the relative atomic mass of O, we need to make the mass of M be the denominator and mass of O be the numerator. is it?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
yep. that's how you convert the given.
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
thank you for correcting my concepts and I am working with part d, I will give you response when I get my answer and you check is my answer correct or not
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
dw:1354708533879:dw observe how i got rid of g O and change it to g M
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
I know it is the answer of part d 168 g M?
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
ummm......what are your steps?
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
g M in MCl = 268.88g5.68g=21.2g M
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
mass ratio is 21.2g M / 5.68g Cl
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
ummmm...you get something wrong.... is 26.88g instead of 268.88g
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
relative mass of Cl = 35.453g
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
just take the relative mass of Cl =35.5g
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
35.5g Cl x 21.2g M / 5.68g Cl = 132.5g M
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
okay I got it. Thank you very much. :)
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
yep. 26.88g  5.68g = 21.2g
 one year ago

kryton1212Best ResponseYou've already chosen the best response.0
1.200 g of a compound containing only C, H and O gave 1.173 g of CO2 and 0.240 g of H2O on complete combustion. Find the empirical formula of the compound.
 one year ago

sirm3dBest ResponseYou've already chosen the best response.1
hmm. 0.213 g O2 used in the process.
 one year ago
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