1. what is the mass percent concentration of a naoh solution formed by mixing 50

Question

1. what is the mass percent concentration of a naoh solution formed by mixing 50ml of a 25.0% (density = 2.45g/ml) Naohsolution with 10.0 mL of water?

2. at 25C what is the osmotic pressure of a homogeneous solution consisting of 21.0 g urea (con2h4;mw=60.0g/mol) diluted with water to 2.50 l?

3.

For the following reaction, P(C 6 H 14 )/ t was found to be -6.20 10 -3 atm/s.? C 6 H 14 (g) C 6 H 6 (g) + 4H 2 (g) Determine the value of P(H 2 )/ t for this reaction at the same time.

Please show steps. Thanks!

Explanation / Answer

2)

moles of urea= n1 = mass /mol. wt = 21/60 = 0.35 moles

Volume of water = 2.50 L = 2500 mL

density = 1 g/mL

so,

wt of water = volume *density = 2500*1 = 2500 g

moles of water = n2 = 2500/18 = 138.8889 moles

mole fraction of solvent = Xs = mole fration of water = n2/(n1+n2) = 138.8889/(138.8889+0.35) = 0.9975

so,

Osmotic pressure = -RT/V*ln(Xs) = -8.314*(25+273.15)/0.0025*ln(0.9975) = 2481.923 Pa

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