Long Answer TypeA welding fuel gas contains carbon and hydrogen only. Burning a small space of it in oxygen gives 3.38 g carbon dioxide, 0·690g of water and no other products. A volume of 10·0L (measured at STP) of this welding gas is found to weigh 11·6g. Calculate: (i) empirical formula (ii) molar mass of the gas and (iii) molecular formula.
i.1mole(44g) of CO2 contains 12g of carbon.
3.38 g of CO2 will contain carbon = (12g/44g) x3.38g =0.9217g
18g of water contains 2g of hydrogen
Therefore 0.690g of water will contain hydrogen=2g/18gx 0.690 =0.0767 g
Since carbon and hydrogen are the only constituents of the compounds, the total mass of the compounds is:
=0.9217+0.767
=0.9984g
Thus,
Percent of C in the compound = (0.9217/.9984) x100 =92.32%
Percent of H in the compound =(0.0767/0.9984) x100=7.68%
Moles of carbon in the compound =92.32/12.00 =7.69
Moles of hydrogen in the compound= 7.68/1=7.68
Since, ration of carbon to hydrogen in the compound=7.69:7.68=1:1
Hence, the empirical formula of the gas is CH.
ii) Given,
Weight of 10.0L of the gas (at S.T.P)=11.6 g
Therefore, weight of 22.4L of gas at STP =(11.6/10.0L) x22.4L
=25.984g
Hence, the molar mass of the gas is 26.0 g.
iii) Empirical formula mass of CH =12+1 =13g
n= molar mass of gas/empirical formula mass of gas
n=26/13
n=2
Therefore, molecular formula of gas= (CH)n
=C2H2
Butyric acid contains only C, H and O, 4.24mg sample of butyric acid is completely burnt. It gives 8.45mg of carbon dioxide and 3.46mg of water. What is the mass percentage of each element in butyric acid?
Short Answer TypeIf the elemental composition of butyric acid is found to be 54.2%C, 9.2%H and 36.6%O, determine the empirical formula.
The molecular mass of butryic acid was determined by experiment to be 88 amu. what is the molecular formula?
Long Answer TypeWhat are the implications of a chemical equation?
Or
What informations are conveyed by a chemical equation?
How can we make a chemical equation more informative?
Or
How can we remove the drawbacks or limitations of a chemical equation?
Short Answer TypeWrite balanced chemical equation for the following reactions making them as informative as you can:
(i) Reaction between magnesium carbonate and dilute sulphuric acid to form an aqueous solution of magnesium sulphate, carbondioxide gas and water.
(ii) Reaction between methane gas (CH4) and oxygen gas to produce carbondioxide, water vapours and heat.
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