## 20 Questions

What is molar concentration also known as?

Molarity

What is the most commonly used unit for molarity?

Moles per liter

How is molarity often depicted?

[M]

What does the variable 'c' represent in the molarity equation?

Number of moles

What is the Avogadro constant defined as since 2019?

$6.02214076×10^23$ particles/mol

What is the coherent unit for molar concentration in the International System of Units (SI)?

mol/m3

When a sodium carbonate solution has a formal concentration of c(Na2CO3) = 1 mol/L, what are the molar concentrations of Na+ and CO2−3?

2 mol/L and 1 mol/L

What is the conversion to mass concentration ρ i given by?

$ρ_i = c_iM_i$

What does the SI prefix 'mega' (symbol M) denote in the context of molar concentration?

Molar

What is the conversion to mole fraction $x_i$ given by?

$x_i = c_iM¯/ρ$

What is the incorrect use of the unit '%' when denoting mass concentration?

Molarity

In thermal engineering, what is used to represent the mass fraction of vapor in the steam?

Vapor quality

What term is used in alloys, especially those of noble metals, to represent the mass fraction of the noble metal in the alloy?

Fineness

What quantity is independent of temperature until phase change occurs?

Mass fraction

What is the ratio of the mass fractions of components in a pure component mixing expressed as?

$w_2 / w_1$

What is the mass fraction of a substance within a mixture represented by?

w_i

How are the mass fractions of the ingredients of a mixture related to the total mass of the mixture?

They sum to unity

In commercial contexts, what is the mass fraction expressed as percentage by mass often called?

Weight percentage (wt.%)

Which term refers to the ratio of the mass of an element to the total mass of a sample?

Mass percent composition

What is another way of expressing the composition of a mixture in a dimensionless size apart from mass fraction?

Mole fraction

## Study Notes

### 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.

Test your knowledge of molar concentration, also known as molarity, and its application in measuring the concentration of solutes in solutions. This quiz covers the unit of molarity, calculations involving molar concentration, and its significance in chemistry.

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