求教:with steps plz :)
1. sodium hydrogencarbonate decomposes on heating according to the following equation : 2 NaHCO3(s) --> NaCO3(s) + CO2 +H2O(l)
what mass of sodium hydrogencarbonate is needed to produce 5.3g of sodium carbonate?
(relative atomic masses: H=1 , C=12 , O=16, Na=23)
2. on heating 12.25 g of KClO3 for 2 minutes, there is a weight loss of 0.96g.
2KClO3(s) ---> 2KCl (s) + 3O2 (g)
what percentage by mass of the original KClO3 has decompesed ?
(relative atomic mass: Cl=35.5 K=39.1 O=16 )
下面呢題睇唔明
3. 5.58g of iron are completely dissolved in excess dilute sulphuric acid . what is
the maximum mass of iron(II) sulphate-7-water obtainable on crystallization?
(relative atomic mass : O=16 H=1 S=32.1 Fe=55.8)
thanks a lot!!
求教:chemistry empirical formula
2012-11-21 5:51 am
回答 (3)
2012-11-21 9:34 am
✔ 最佳答案
Q1 . no. of mole of sodium carbonate = 5.3/(23x2+12+16x3) = 0.05 mol2 mole of sodium hydrogencarbonate can form 1 mole of sodium carbonate
mass of sodium hydrogencarbonate = 0.05x2x(23+1+12+16x3) = 8.4 g
Q2 . no. of mole of CO2 formed = 0.96/(12+16x2) = 0.016 mol
mass of mole of KClO3 decomposed = 0.016x(2/3)x(39.1+35.5+16x3) = 1.3077 g
percentage by mass = 1.3077/12.25 x 100%= 10.675%
Q3 . Fe + H2SO4 + 7 H2O --> FeSO4 ∙7H2O + H2
no. of mole of Iron dissolved = 5.58/55.8 = 0.1 mol
no. of mole of FeSO4 ∙7H2O formed = 0.1 mol
the maximum mass of FeSO4 ∙7H2O = 0.1x(55.8+32.1+16x4+7x(16+2)) = 27.79 g
參考: me
2012-11-22 5:30 am
Q2 ans:20%
2012-11-21 8:09 pm
2.
2KClO3(s) → 2KCl(s) + 3O2(g)
No. of moles of O2 released = 0.96/(16 x 2) = 0.03 mol
No. of moles of KClO3 decomposed = 0.03 x (2/3) = 0.02 mol
Mass of KClO3 decomposed = 0.02 x (39.1 + 35.5 + 16x3) = 2.452 g
% by mass of KClO3 decomposed = (2.452/12.25) x 100% = 20% ...... (answer)
2KClO3(s) → 2KCl(s) + 3O2(g)
No. of moles of O2 released = 0.96/(16 x 2) = 0.03 mol
No. of moles of KClO3 decomposed = 0.03 x (2/3) = 0.02 mol
Mass of KClO3 decomposed = 0.02 x (39.1 + 35.5 + 16x3) = 2.452 g
% by mass of KClO3 decomposed = (2.452/12.25) x 100% = 20% ...... (answer)
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