Examples of molar mass in the following topics:
-
- Molar mass (M) is equal to the mass of one mole of a particular element or compound; as such, molar masses are expressed in units of grams per mole (g mol–1) and are often referred to as molecular weights.
- To find the molar mass of a mixture of gases, you need to take into account the molar mass of each gas in the mixture, as well as their relative proportion.
- The average molar mass of a mixture of gases is equal to the sum of the mole fractions of each gas, multiplied by their respective molar masses:
- where m is the mass of the gas, and M is the molar mass.
- What is the molar mass of the gas?
-
- The molar mass of a particular substance is the mass of one mole of that substance.
- Molar mass is the mass of a given substance divided by the amount of that substance, measured in g/mol.
- The characteristic molar mass of an element is simply the atomic mass in g/mol.
- However, molar mass can also be calculated by multiplying the atomic mass in amu by the molar mass constant (1 g/mol).
- The molar mass of NaCl is 58.44 g/mol.
-
- Mass-to-mole conversions can be facilitated by employing the molar mass as a conversion ratio.
- The molar mass value can be used as a conversion factor to facilitate mass-to-mole and mole-to-mass conversions.
- For a single element, the molar mass is equivalent to its atomic weight multiplied by the molar mass constant (1 g/mol).
- For a compound, the molar mass is the sum of the atomic weights of each element in the compound multiplied by the molar mass constant.
- The molar mass of water is 18 g/mol.
-
- A substance's molar mass can be used to convert between the mass of the substance and the number of moles in that substance.
- For example, if the atomic mass of sulfer (S) is 32.066 amu, then its molar mass is 32.066 g/mol.
- In a compound of NaOH, the molar mass of Na alone is 23 g/mol, the molar mass of O is 16 g/mol, and H is 1 g/mol.
- What is the molar mass of NaOH?
- Since the molar mass of NaOH is 40 g/mol, we can divide the 90 g of NaOH by the molar mass (40 g/mol) to find the moles of NaOH.
-
- If the amount of solute is given in grams, we must first calculate the number of moles of solute using the solute's molar mass, then calculate the molarity using the number of moles and total volume.
- First, we must convert the mass of NaCl in grams into moles.
- We can also calculate the volume required to meet a specific mass in grams given the molarity of the solution.
- This is useful with particular solutes that cannot be easily massed with a balance.
- First we must convert grams of BH3 to moles by dividing the mass by the molecular weight.
-
- In chemistry, molar concentration, or molarity, is defined as moles of solute per total liters of solution.
- The SI unit for molarity is is mol/m3; however, you will almost always encounter molarity with the units of mol/L.
- This video demonstrates practice problems with molarity, calculating the moles and liters to find the molar concentration.
- Use molarity to convert between mass and volume in a solution.
- This video looks at how to use molarity as a conversion factor.
-
- Unlike molarity, which depends on the volume of the solution, molality depends only on the mass of the solvent.
- Since volume is subject to variation due to temperature and pressure, molarity also varies by temperature and pressure.
- Molality is based on mass, so it can easily be converted into a mass ratio, denoted by w:
- Compared to molar concentration or mass concentration, the preparation of a solution of a given molality is easy because it requires only a good scale; both solvent and solute are massed, rather than measured by volume.
- In this lesson, you will learn how molarity and molality differ.
-
- Therefore, for a mass-to-mass conversion, it is necessary to first convert one amount to moles, then use the conversion factor to find moles of the other substance, and then convert the molar value of interest back to mass.
- Taking coefficients from the reaction equation (13 O2 and 2 C4H10), the molar ratio of O2 to C4H10 is 13:2.
- The molar amount of O2 can now be easily converted back to grams of oxygen:
- But by converting the butane mass to moles (0.929 moles) and using the molar ratio (13 moles oxygen : 2 moles butane), one can find the molar amount of oxygen (6.05 moles) that reacts with 54.0 grams of butane.
- Using the molar amount of oxygen, it is then possible to find the mass of the oxygen (193 g).
-
- Heat capacity is an extensive property, meaning that it is dependent upon the size/mass of the sample.
- Units of molar heat capacity are $\frac{J}{K\bullet mol}$.
- In these equations, m is the substance's mass in grams (used when calculating with specific heat), and n is the number of moles of substance (used when calculating with molar heat capacity).
- The molar heat capacity of water, CP, is 75.2 $\frac{J}{mol\bullet K}$.
- We are given the molar heat capacity of water, so we need to convert the given mass of water to moles:
-
- Molar ratios, or conversion factors, identify the number of moles of each reactant needed to form a certain number of moles of each product.
- Because the law of conservation of mass dictates that the quantity of each element must remain unchanged over the course of a chemical reaction, each side of a balanced chemical equation must have the same quantity of each particular element.
- From this reaction equation, it is possible to deduce the following molar ratios:
- These molar ratios can also be expressed as fractions.
- Calculate the molar ratio between two substances given their balanced reaction