Reacting Masses

2014-11-27 7:51 am

1. Find the empirical formula of a compound of 43.4% sodium, 11.3% carbon and 45.3% oxygen by mass.

2. The composition percentage by mass of compound Y is Zn : 40.5%; S : 19.85%and O : 39.65%. Find its empirical formula.

3. On reduction, 0.36g of an oxide gives 0.31g of lead. Find the empirical formula of the oxide.

4. Copper oxide is reduced by hydrogen. What mass of copper will be produced from : 3.6g of copper(II) oxide ?

回答 (1)

用戶26240

2014-11-27 10:18 am

✔ 最佳答案

1.
Mole ratio Na : C : O
= 43.4/23 : 11.3/12 : 45.3/16
= 1.89 : 0.942 : 2.83
= 2 : 1 : 3

Empirical formula = Na2CO3

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2.
Mole ratio Zn : S : O
= 40.5/65.4 : 19.85/32 : 39.65/16
= 0.619 : 0.620 : 2.48
= 1 : 1 : 4

Empirical formula = ZnSO4

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3.
Mass of Pb = 0.31 g
Mass of O = 0.36 - 0.31 = 0.05 g

Mole ratio Pb : O
= 0.31/207 : 0.05/16
= 0.00150 : 0.00313
= 1 : 2

Empirical formula = PbO2

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4.
Mass of 1 mole of CuO = 63.5 + 16 = 79.5 g
Mass of Cu in 1 mole CuO = 63.5 g

Mass of Cu produced
= 3.6 × (63.5/79.5)
= 2.88 g

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