Answer:
1.0555 * 10^24 molecules
Explanation:
Number of molecules = ?
Mass = 3.79 Kg = 3790 g
Molar mass of Cs7(Cr5O3)4 = 2162.25 g/mol
Number of moles = Mass / Molar mass
Number of moles = 3790 g / 2162.25 g/mol
Number of moles = 1.7528 mol
1 mol = 6.022 * 10^23 molecules
1.7528 mol = x
solving for x;
x = 6.022 * 10^23 * 1.7528
x = 1.0555 * 10^24 molecules
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Molar mass of FE2O3=2(55.85)+3(16)=159.7
2.56g*1mol/159.7*2mol/1mol*55.85g/1mol=1.79g
<span>(4) The dissolving of the LiBr(s) in water is an exothermic process</span>
Answer:
The final temperature of the solution is 44.8 °C
Explanation:
assuming no heat loss to the surroundings, all the heat of solution (due to the dissolving process) is absorbed by the same solution and therefore:
Q dis + Q sol = 0
Using tables , can be found that the heat of solution of CaCl2 at 25°C (≈24.7 °C) is q dis= -83.3 KJ/mol . And the molecular weight is
M = 1*40 g/mol + 2* 35.45 g/mol = 110.9 g/mol
Q dis = q dis * n = q dis * m/M = -83.3 KJ/mol * 13.1 g/110.9 gr/mol = -9.84 KJ
Qdis= -9.84 KJ
Also Qsol = ms * Cs * (T - Ti)
therefore
ms * Cs * (T - Ti) + Qdis = 0
T= Ti - Qdis * (ms * Cs )^-1 =24.7 °C - (-9.84 KJ/mol)/[(104 g + 13.1 g)* 4.18 J/g°C] *1000 J/KJ
T= 44.8 °C
