How many moles of calcium are in a 351 kg sample?

351 kg = 351 x 1000 = 351000 grams

number of moles can be calculated using the following rule:

number of moles = mass / molar mass

From the periodic table:

molar mass of calcium = 40.078 grams

Therefore, substituting in the above equation:

number of moles = 351000 / 40.078 = 8757.922 moles