Question

the atomic mass of the element niobium (nb) is 92.906 amu. which measurement is correct? (1 point)
1 mole of nb = 92.906 grams
1 mole of nb = 92.906 atoms
1 gram of nb = 92.906 atoms
1 gram of nb = 92.906 moles

Explanation:

• The atomic mass of an element in atomic mass units (amu) is numerically equal to its molar mass in grams per mole ($g/mol$). So, if the atomic mass of niobium ($Nb$) is $92.906$ amu, then the molar mass of $Nb$ is $92.906\ g/mol$. By definition, 1 mole of a substance has a mass equal to its molar mass. So, 1 mole of $Nb$ has a mass of $92.906$ grams.
• 1 mole of any substance contains $6.022\times 10^{23}$ atoms (Avogadro's number), not $92.906$ atoms. So, the statement “1 mole of $Nb = 92.906$ atoms” is incorrect.
• To find the number of atoms in a given mass of an element, we use the formula $n=\frac{m}{M}\times N_A$, where $n$ is the number of moles, $m$ is the mass, $M$ is the molar mass, and $N_A$ is Avogadro's number ($6.022\times 10^{23}\ atoms/mol$). For $m = 1\ g$ and $M=92.906\ g/mol$ of $Nb$, $n=\frac{1}{92.906}\ mol$ and the number of atoms $N=\frac{1}{92.906}\times6.022\times 10^{23}\ atoms

eq92.906\ atoms$. So, the statement “1 gram of $Nb = 92.906$ atoms” is incorrect.

• Using the formula $n=\frac{m}{M}$, for $m = 1\ g$ and $M = 92.906\ g/mol$ of $Nb$, $n=\frac{1}{92.906}\ mol

eq92.906\ mol$. So, the statement “1 gram of $Nb = 92.906$ moles” is incorrect.

Answer:

1 mole of $Nb = 92.906$ grams