   Chapter 11, Problem 130IP

Chapter
Section
Textbook Problem

# Creatinine, C4H7N3O, is a by-product of muscle metabolism, and creatinine levels in the body are known to be a fairly reliable indicator of kidney function. The normal level of creatinine in the blood for adults is approximately 1.0 mg per deciliter (dL) of blood. If the density of blood is 1.025 g/mL, calculate the molality of a normal creatinine level in a 10.0-mL blood sample. What is the osmotic pressure of this solution at 25.0°C?

Interpretation Introduction

Interpretation: The molality of normal Creatinine solution and osmotic pressure at 25°C has to be calculated.

Concept Introduction:

Molality of a solution also called as molal concentration can be defined as the mass of solute in grams to the mass of the solvent in kilograms. It can be given by the equation,

Molality(molkg-1)=Massofsolue(ing)Massofsolvent(inkg)

When a semipermeable membrane, separates a solution and pure solvent. The solvent molecules are passed through the semi permeable membrane. There is gradual increase in the volume of solution with a decrease in volume of the solvent with respect to time. The flow of solvent through a semipermeable membrane into the solution is called as osmosis. By the time system reaches equilibrium, the changes in the liquid level stops. There is a higher hydrostatic pressure on the solution than compared to that of the pure solvent because there is variation in the liquid levels at this point. The excess pressure on the solution is called osmotic pressure.

The osmotic pressure of solution is calculated by using,

Π=MRT

Here,

Π=osmoticpressure(in atm)

M=molarityofsolution(inM)

R=Gasconstant

T=Temperature(inK)

Explanation

Record the given data

Density of blood = 1.025gmL-1

Mass of Creatinine in blood   = 1.0mgperdL

Volume of Creatinine in blood = 10.0mL

To calculate the moles of Creatinine

Molar mass of Creatinine= 113.13g

Moles of Creatinine =

10.0mLblood×1L1000mL×10dL1L×1.0mgC4H7N3O1dLblood×1g1000mg×1molC4H7N3O113.13g

= 8.8×10-7mol

Moles of Creatinine= 8.8×10-7mol

To calculate the mass of blood

Mass of blood = 10.0mL×1.025gmL

= 10.3g

Mass of blood = 10.3g

To calculate the molality of Creatinine in blood

Mass of blood = 10.3g

Moles of Creatinine= 8.8×10-7mol

Molality of Creatinine = 8

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