Question

how many moles of chloride ions are in 0.0750 g of magnesium chloride ?

Answer 1

Answer: 1.85 x 10^21

Always remember 1 mole of ANY atoms or molecules refer to 6.02 x 10^23 atoms or molecules

just like a dozen eggs mean 12 eggs

a mole of eggs mean 6.02 x 10^23 eggs

so 1 mole of chloride ions means there are 6.02 x 10^23 chloride ions

And one mole of chloride weighs 24.31g ( its usually given in the question or in the sheet )

0.0750 g x (6.02 x 10^23 # chloride ions / 24.31 g )  

here 6.02 x 10^23 chloride ions weights 24.31 g so we use this ratio  and the grams cancel out// giving us the number of chloride ions