Hi,
I really need help in this 2 questions... homework of em due tomorrow at 8 am...ma` em bi. stuck on this questions:

1) A certain stock of phosphoric acid solution is 40% by mass and has a specific gravity of 1.40. What is the molarity of the solution?

2) a 1.500g sample of a mixture containing only Cu2O and CUO was treated with hydrogen gas to produce 1.216 pure copper metal calculate % composition by mass of the mixture.
CU2O + H2 ---> 2CU + H2O (rxn. 1)
CUO + H2 ---> CU + H2O (rxn. 2)

Note: One mixture but two different mole to mole ratio with products.

Ne'u ai giu'p duo.c em ca'm on nhie`u that la` nhie`
Em nhut dau ve` chemistry qua' luon!!

Bài quá đơn giản, đáng lý bạn phải suy nghĩ thêm một chút.
1/ Density = 1.40 => 1 L = 1400 g
Conc. = 40% (w) => 1400 g * 40% = 560 g H3PO4
H3PO4 : 1 mol = 98 g, 560 g = 5.71
Solution is 5.71 mol / L or 5.71 M

2/ x : % of Cu2O, 1 - x, % of CuO.
Cu2O = 64*2 + 16 = 144 (g/mol)
CuO = 64 + 16 = 80 (g/mol)

The mass of Cu produced by reaction 1 :
1500 * x * (128/144)
The mass of Cu produced by reaction 2 :
1500 * (1-x) * (64/80)

Tổng lượng Cu : 1500 * x * (128/144) + 1500 * (1-x) * (64/80) = 1216
<=> 133.3333 x = 16 <=> x = 0.12
Vậy có 12% Cu2O, 88% CuO.

wow Bouh nhớ mấy công thức hay ghê...

TSDP học thì biết và nhớ..chứ giờ hỏi lại thì chịu thua...