Question

a 52 - kg woman has 7.2×10⁻³ mol of hemoglobin (molar mass = 64456 g/mol) in her blood. what quantity of hemoglobin molecules is this? starting amount × ( )

Explanation:

Step1: Identify the given information

We are given that there are $7.2\times10^{17}$ mol of hemoglobin in the blood and we want to convert moles to molecules. We use Avogadro's number which is $6.022\times 10^{23}$ molecules/mol.

Step2: Set up the conversion

The number of molecules $N$ of a substance in moles $n$ is given by the formula $N=n\times N_A$, where $N_A = 6.022\times 10^{23}$ molecules/mol. Here, $n = 7.2\times10^{17}$ mol.
So, $N=(7.2\times 10^{17}\text{ mol})\times(6.022\times 10^{23}\text{ molecules/mol})$

Step3: Calculate the result

Using the rule of exponents $a^m\times a^n=a^{m + n}$, we have $N=(7.2\times6.022)\times10^{17 + 23}=43.3584\times10^{40}=4.33584\times 10^{41}$ molecules.

Answer:

$4.3\times 10^{41}$ molecules of hemoglobin (rounded to 2 significant - figures as 7.2 has 2 significant - figures)