Mole cal. Chemistry

2011-10-10 6:48 am

Magnesium nitrate decomposes on heating to form magnesium oxide, nitrogen dioxide and oxygen as shown in the following equation.

2Mg(NO3)2 (s) > 2MgO(s) + 4NO2(g) + O2(g)

(a) thermal decompsoition of a sample of magnesium nitrate produced 0.741g of magnesium oxide.

(a.i) calculate the amount, in moles of MgO in 0.741g of magnesium oxide.
Answer: 0.018moles <-- 呢part我識下part就吾明

(a.ii) calculate the total amount, in moles, of gas produced from this sample of magesium nitrate
n(Mg(NO3)2)= 0.018 X 5/2 <------------- 點解要乘5/2,,, 請解釋... 吾明

回答 (1)

知識就是力量

2011-10-10 6:57 am

✔ 最佳答案

Mole ratio between [Mg(NO3)2 or MgO] and gas produced [NO2 and O2]
= 2 : (4 + 1)
= 2 : 5
Hence total number of moles of gas produced
= [no. of moles of Mg(NO3)2 or MgO] * 5/2
= 0.018 * 5/2
= 0.045 mol

參考: Knowledge is power.

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