Molar Concentration and Solution Composition Quiz

Molarity and Concentration

• Molar concentration is also known as molarity.
• The most commonly used unit for molarity is moles per liter (mol/L).
• Molarity is often depicted as M (capital M).
• In the molarity equation, the variable 'c' represents the concentration in moles per liter.
• Since 2019, the Avogadro constant is defined as 6.02214076 x 10^23 particles (atoms or molecules).

Concentration Calculations

• When a sodium carbonate solution has a formal concentration of c(Na2CO3) = 1 mol/L, the molar concentrations of Na+ and CO2−3 are 2 mol/L and 1 mol/L, respectively.
• The conversion to mass concentration ρ i is given by ρi = M_i * c_i, where M_i is the molar mass of the substance.
• The conversion to mole fraction $x_i$ is given by xi = c_i / Σc_j, where j represents all components.

Units and Notations

• The SI prefix 'mega' (symbol M) denotes 10^6 in the context of molar concentration.
• The coherent unit for molar concentration in the International System of Units (SI) is moles per liter (mol/L).

Other Concentration Units

• In thermal engineering, the mass fraction of vapor in the steam is represented by x.
• In alloys, especially those of noble metals, the mass fraction of the noble metal in the alloy is represented by the term "fineness".
• The mass fraction of a substance within a mixture is represented by wi.

Relationships Between Concentrations

• The mass fractions of the ingredients of a mixture are related to the total mass of the mixture by Σwi = 1.
• In commercial contexts, the mass fraction expressed as percentage by mass is often called percentage composition.
• The ratio of the mass fractions of components in a pure component mixing is expressed as wi / wj.
• Another way of expressing the composition of a mixture in a dimensionless size apart from mass fraction is mole fraction.
• The term "assay" refers to the ratio of the mass of an element to the total mass of a sample.