Chem 求救[+good]

冷冷雨~WoWo

1.        What is the empirical formula of a compound which is made up of 37.5% carbon, 12.5% hydrogen, and the rest made up of oxygen.

2.        Sodium reacts with water producing sodium hydroxide and hydrogen gas.
(a) Write the equation for the reaction.
(b) What volume of hydrogen is produced at r.t.p. when 0.2 mol of sodium reacts?

3.        The reaction between hydrochloric acid and calcium carbonate is shown.
2HCl + CaCO3 → CaCl2 + H2O + CO2
What volume of 1M hydrochloric acid is needed to react completely with 1.0g of calcium carbonate?

4.        Propane burns completely in oxygen according to the equation shown
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)
If 0.1 mol of propane gas is burnt completely, what volume of gaseous product is obtained, measured at room temperature and pressure?

5.        What mass of calcium oxide could be obtained by heating 25g of CaCO3.
CaCO3 → CaO + CO2

6.        Hydrocarbons A and B both contain 85.7% carbon and 14.3% hydrogen.
(a) Find the empirical formula of A and B
(b) Find the molecular formula of A and B if the molecular mass (Mr) of A is 42 g and the molecular mass of B is 84.

7.        What is the percentage yield of the reaction if 51 kg of aluminium oxide produced 17 kg of aluminium?
2Al2O3(l) → 4Al(l) + 3O2(g)

8.        A 4.0g sample of dry ice (solid CO2) turned into 1900cm3 of carbon dioxide gas at rtp. What was the percentage purity of the dry ice?

9.        What volume of ammonia gas would be needed to produce 35 g of ammonium nitrate in the following reaction?
NH3(g) + HNO3(aq) → NH4NO3(aq)

10.         What mass of magnesium would be needed to produce 150 cm3 of hydrogen?
Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)

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〝Ex喵﹑

睇唔明英文

冷冷雨~WoWo

〝Ex喵﹑ 發表於 12-1-19 12:03 AM
睇唔明英文

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postpet40

全部都識做...
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postpet40

第1條係C H4 O methanol

冷冷雨~WoWo

postpet40 發表於 12-1-19 12:26 AM
第1條係C H4 O methanol

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冷冷雨~WoWo

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BOBBBY5555255

自己禁機
1.        What is the empirical formula of a compound which is made up of 37.5% carbon, 12.5% hydrogen, and the rest made up of oxygen

let the compound be 100g

mass ratio   C          :     H        :   O
mole ratio   37.5/12   12.5/1     (100-37.5-12.5)/16
                              :                :
therefore, the empirical formula of the compound is ______________
  



2.        Sodium reacts with water producing sodium hydroxide and hydrogen gas.
(a) Write the equation for the reaction.
(b) What volume of hydrogen is produced at r.t.p. when 0.2 mol of sodium reacts?

a)2Na + 2H2O > 2NaOH + H2  (METAL + WATER > METAL HYDROXIDE + HYDROGEN)

b)no of mole of Na= 0.2mol
   no of mole of H2=0.1mol(  ratio Na:H2= 2:1)
PV=nRT
V=nRT/P   (R=8.31)
V=(0.1*8.31*(25+273))/1.01*10 ^3            8.31 , kPa, m3, mole, K(298)
V=___ m
V=____dm3

3.        The reaction between hydrochloric acid and calcium carbonate is shown.
2HCl + CaCO3 → CaCl2 + H2O + CO2
What volume of 1M hydrochloric acid is needed to react completely with 1.0g of calcium carbonate?
no of mole of CaCO3 = 1/(40.1+12+16*3)=    mol
no of mole of HCl       =  ____ X2   =     mol
volume of 1M HCl      =____X1      =      dm3


4.        Propane burns completely in oxygen according to the equation shown
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)
If 0.1 mol of propane gas is burnt completely, what volume of gaseous product is obtained, measured at room temperature and pressure?

Refer to  Q2

5.        What mass of calcium oxide could be obtained by heating 25g of CaCO3.
CaCO3 → CaO + CO2

Refer to Q3

6.        Hydrocarbons A and B both contain 85.7% carbon and 14.3% hydrogen.
(a) Find the empirical formula of A and B
(b) Find the molecular formula of A and B if the molecular mass (Mr) of A is 42 g and the molecular mass of B is 84.

a) Refer to Q1

b) A (CnHm)x=42   B (CnHm)x=84



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第10題
150cm^3 gas=3/448 mol (stp)
ratio=Mg:H2=1:1
=3/448x24.3
=0.162723214g