A crystalline sample has a mass of 6.50g and is composed purely of NaCl (molar mass 58.44gmol−1). Approximately how many formula units of NaCl are in the sample?
a) 1.10×1023 formula units
b) 1.03×1022 formula units
c) 6.70×1022 formula units
d) 6.70×1021 formula units