1. 24.4 g of hydrated metal sulphate were heated to a constant mass. After colling to room temperature, the anhydrous metal sulphate weighed 11.9 g. How many moles of water crystallization are there in one mole of the hydrated metal sulphate?(Relative formula/ molecular masses: hydrated metal sulphate=120.4, water=18.0)
2. the formula of hydrated sodium carbonate crystals is Na2CO3‧xH2O. When 66.9 g of the hydrated crystals are heated, 24.8 g of anhydrous sodium carbonate are produced. What is the value of x? (Relative atomic masses: H=1.0, C=12.0, O=16.0, Na=23.0)
3. the formula of hydrated zinc sulphate is ZnSO4‧xH2O. On strong heating, 18.7 g of the hydrated sulphate produces 8.19 g of water. What is the value of x? (Relative atomic masses: H=1.0, O=16.0, S=32.1, Zn=65.4)
4. Alumimium can be produced from aluminum oxide by the following reaction:Al2O3+3Mg(s)→2Al(s)+ 3MgO(s)What mass of aluminum oxide is required to produce 11.9 g of aluminum?(Relative atomic masses: O=16.0, Al=27.0)
5. A solid mixture consists of 1.0mole of calcium carbonate and 1.0mole of sodium carbonate. What is the least number of moles of hydrochloric acid required to liberate all the carbon dioxide from the mixture?
6. Ammonium dichromate ((NH4)2Cr2O7) decomposes on heating to give chromium (III) oxide, water and nitrogen. What mass of water is obtained when 277Gof (NH4) Cr2O7 undergo complete decomposition? (Relative atomic masses: H=1.0, N=14.0, O=16.0, Cr=52.0)
7. the following equation represents the reaction of propane (C3H8) with oxygen:C3H8(g)+5O2(g) →3CO2(g)+4H2O(l)What is the mass of carbon dioxide formed when 3 moles of propane react with 10moles of oxygen? (Relative atomic masses: C=12.0, O=16.0)
請列出全部長解及答案才給積分~~
攞命難題(Chemistry) 7條
2008-11-08 11:18 pm
回答 (2)
2008-11-10 8:50 am
✔ 最佳答案
1)(hydrated metal sulphate - anhydrous metal sulphate)/molecular masses H2O
(24.4-11.9)/18 =0.69MOL OF H2O
2)
(66.9-24.8)/18 MOL =42.1/18 mol H2O ...a
mol anhydrous sodium carbonate =24.8/(23*2+12+16*3)=24.8/106 mol...b
b:a=24.6/106:42.1/18
=1:10,X=10
3)(18.7-8.19)/18=10.51/18 mol H2O...a
8.19/(65+32+16*4)=8.19/161 mol ZnSO4....b
b:a=:8.19/161:10.51/18
=1:5
X=5
4)mol al=11.9/27mol AL...a
a*(27*2+16*3)=11.9*102/27=44.96g of aluminum oxide required.
5)4mol .since 1 mol CO3(2-) react with 2 mol H+.
6)277/((14+4)*2+52*2+16*7)=277/525 mol ((NH4)2Cr2O7)...a
a*4/2=277*2/525=1.06mol H2O(since 1 mol of ((NH4)2Cr2O7) have 4 H atom, and each 2 H atom give 1 H2O.)
7)mol Catoms =3*3=9
mol O2=10
mol CO2=9,since 1 mol C atoms react with 1 mol O2
9mol CO2*(12+16*2)g/mol=396g
作為考試作答應該已經係長解
如果唔夠,每題一開始自己加上n=M/m 之類公式.
呢D功課最好自己做啦
參考: 自己
2008-11-12 10:17 pm
7. the following equation represents the reaction of propane (C3H8) with oxygen:C3H8(g)+5O2(g) →3CO2(g)+4H2O(l)What is the mass of carbon dioxide formed when 3 moles of propane react with 10moles of oxygen? (Relative atomic masses: C=12.0, O=16.0)
Ans:
From equation
1mole of C3H8 react with 5 moles of O2 to form 3 moles CO2 and 4moles water
therefore only 2 moles of C3H8 can react with 10moles of O2, so 6moles of CO2 is formed. 6*(12+32)= 264gm CO2 .
2008-11-12 14:21:06 補充：
In fact, if 3 mole C3H8 react with 10 moles of O2, it is a imcomplete combustion, C dust will form.
Ans:
From equation
1mole of C3H8 react with 5 moles of O2 to form 3 moles CO2 and 4moles water
therefore only 2 moles of C3H8 can react with 10moles of O2, so 6moles of CO2 is formed. 6*(12+32)= 264gm CO2 .
2008-11-12 14:21:06 補充：
In fact, if 3 mole C3H8 react with 10 moles of O2, it is a imcomplete combustion, C dust will form.
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