Answer
1.814molesPbSO4
Explanation:
You can go from moles of a given substance to grams or vice versa by using the molar mass of said substance.
The molar mass tells you the mass of 1 mole of a given substance
The molar mass tells you the mass of 1 mole of a given substance
Molarmass=massingrams1moleofsubstance
In your case, lead(II) sulfate, PbSO4 has a molar mass of 303.2626gmol−1 which means that every mole of lead(II) sulfate has a mass of 303.2626 g.
To convert from grams to moles, set up the molar mass as a conversion factor with the mass of 1 mole as the denominator
1molePbSO4303.2626g
You will have
550.0g.1molePbSO4303.2626g=1.814molesPbSO4
The answer is rounded to four sig figs.