Why active mass of pure solid or pure liquid is constant?

For solids and liquids the active mass is unity. Reason: The active mass of pure solids and liquids depends on the density and molecular mass. The density and molecular of a mass of pure liquids and solids are constant.

What is active mass and active mass?

Definition of active mass 1 : the concentration of a reacting substance expressed usually in moles per liter. 2 : the concentration of the portion of a dissolved electrolyte that is dissociated into ions and hence is capable of carrying the electric current.

What is the active mass of pure water?

Why is the active mass of water is 55.5?

Why is the activity of solids and liquids 1?

Because the standard state of solids and liquids is their molar density at room temperature and pressure, which is equal to their “concentrations” anyway. So, a≈1 for pure solids and liquids sufficiently close to 25∘C and #”1 bar”.

Why active mass of solid is unity?

For solids or liquids, as mass decreases the volume also decreases by a proportional amount. 1000L water and 10mL water both have molar densities of 55.5 mol/L. So molar density variations are minimum and hence the variations in molar activity is minimum. So the activity coefficient is taken as unity.

Is active mass and molarity same?

Active mass can be thought of as the amount of reactants actually taking part in the reaction. For calculation purposes we take, active mass= molarity. Active mass is the concentration of a reacting substance expressed usually in moles per liter and it is same as molarity… There is no difference generally!

What is active mass of solid?

Active mass is defined as the molar concentration ie. number of Gram-moles per litre. Active mass of pure solid/liquid is always 1 . Molar concentration is directly proportional to density.

Why pure liquids and solids can be ignored while writing the equilibrium constant expression?

The concentration of pure liquids and solids in the equilibrium expression for heterogeneous reactions are ignored because their concentrations remain constant. By convention, the concentration of all pure solids and pure liquids is taken as unity, i.e. (a) Write an expression for Kp for the above reaction.

What is the active mass of solid?

Active mass of pure solid/liquid is always 1 . Molar concentration is directly proportional to density. Since density of solid or liquid always remains constant, the active mass is taken as 1 .

Why does the concentration of a solid and liquid take constant?

That is because the density of liquids and solids is temperature and pressure dependent. The reason that the molar concentration is often called constant is twofold: the density of liquids and solids has a much weaker dependence on the temperature than gases do therefore it can be regarded as approximately constant.

What is the activity of a solid?

For all solids, the activity is a ratio of the concentration of a pure solid to the concentration of that same pure solid. asolid=Ceffective solidCºeffective solid=1. asolid always has a value of 1 with no units.

Why is the concentration of solid 1?

When a solid or liquid is consumed in a reaction, the number of molecules drops, but so does the space they take up. So their concentration really is constant.

Why is the active mass of pure solids and pure liquids constant?

The active mass of solids and pure liquids is a constant quantity (unity) and solvent (excess) is considered as one. Because there is no change in activity with the change in quantity or volume of vessel. as density of pure solids and liquids is constant and molecular mass is also constant.

Can the law of mass action be applied to solids?

The law of mass action can be applied to a reversible reaction to derive a mathematical expression for the equilibrium constant, known as the law of chemical equilibrium. The Law of mass action cannot be applied for pure solids and pure liquids, and even solid-state or liquid state substances.

What is the difference between active mass and active mass?

$\\begingroup$@AdeshTamrakar “activity” is dimensionless. “active mass” is a historical term that professional chemists do not use anymore. The correct historical meaning of “active mass” is mass per volume, such as mass per cubic centimeter.

What is the difference between concentration and activity in chemistry?

Activity has different meanings in different contexts. pls specify which one you wanna know. Concentration = Mass / Volume. Mass is constant. for solids and liquids, volume is also constant as they are incompressible. So concentration is constant and is taken to be unity.