Question
Question: A 120 grams \({\text{NaCl}}\) is equal to how many molecules of \({\text{NaCl}}\)?...
A 120 grams NaCl is equal to how many molecules of NaCl?
Solution
The mole concept is used to determine the amount of the substance which is obtained by taking the ratio of the mass of the substance to the molecular mass of the substance.
One mole of the substance contains the Avogadro’s numbers of the particles that are atoms, ions, or molecules of the substance.
Avogadro’s number is represented as NA. The value of Avogadro’s number is 6.023×1023molecules.
Formula used: The mole of the substance contains Avogadro’s numbers of molecules.
1mole = NA = 6.023×1023molecules
Complete step by step answer:
Here, the molecular weight of the NaCl given is 58.44g/mol and the weight of the NaCl is 120 grams.
We have to determine the first moles of the NaClin 120 gram as follows:
⇒moles = Molecularweightweight
Substitute, 58.44g/mol for molecular weight and 120 gram for weight.
⇒moles = 58.44g/mol120g
moles = 2.0534mol
Thus, the moles of the NaCl in 120 gram are 2.0534mol.
Now, determine the molecules of the NaCl in the o120 gram as follows:
As we know that one mole of the substance contains Avogadro’s numbers of molecules.
⇒1mol = NA = 6.023×1023molecules
⇒2.0534mol = 1mol2.0534mol×6.023×1023molecules
⇒2.0534mol = 1.2367×1024molecules
Thus, the molecules of NaClin 120 gram are 1.24×1024.
Note: Molecular weight is the average mass of the molecules and it is deferrable from molecule to molecule. In the case of the atom, it is called atomic mass while in the case of the molecular mass it is calculated by taking the sum of the atomic masses of all the atoms in the molecule. Here, we have to use the molecular weight of the NaCl. The SI unit of the molecular weight is gram per mole. Its unit itself indicates the ratio of the mass of the substance to the molar molecular mass of the substance.