中四Chem 題目

🎓 學業台教學

[匿名]

2011-08-26 10:45 pm

1) On mixing 50g calcium nitrate solution and 50g potassium carbonate solution, 5.00g precipitate is obtained.
(a) Write the equation between calcium nitrate and
potassium carbonate.
(b) Calculate the mass of calcium nitrate in the solution.
(c) Before weighing the precipitate, it is necessary to carry
out filtration, washing and drying. State in details how
you wash the precipitate obtained.

2) Work out the formula of magnesium nitride, in which 3.6g
of magnesium combines with 1.4g of nitrogen.

更新1:

是不懂怎樣做, 而唔係唔做 =.=

回答 (2)

不想單身

2011-09-05 9:03 pm

✔ 最佳答案

絕對明白閣下是想請教而不是想請槍
由於我放低chem已經有幾年,盡量幫助你吧

1.(a) CaNO3 + KCO3 --> KNO3 + CaCO3
(b) no. of mole of KNO3 = mass / molar mass
= 5 / (39.1+ 14 +16x3) = 0.0495 mol
So, mass of CaNO3 = no. of mole x molar mass
= 0.0495 x (40 +14 +16x3) = 5.0445 g
(c) 1.wash the precipitate with acid
2. then wash with distillated water
3. put it under sun, and wait for about 3hours for dry.

2. 2 Mg + 2 N + 3 O2 --> 2 MgNO3

有d答案唔肯定, 但希望幫到你 :)

參考: me

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用戶2151

2011-08-30 11:51 pm

You should do you homework, you lazy bug!

參考: myself

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