How many moles of NaCl (NW =58 g) are in 29 microgram of NaCl?

Question

How many moles of NaCl (NW =58 g) are in 29 microgram of NaCl?

a,5 x 10^-7 moles

 

  b, 5 x 10^-5 moles

 

  c, 2 x 10^-7 moles

 

 d, 2 x 10^-6 moles

 

Answer 1

Since all the options are given in moles (as opposed to millimoles, micromoles, etc.) we will work in grams so it's easy to then convert to moles. Recall that 1 g = 10⁶ ug

29 ug NaCl x 1 g / 1x10⁶ ug = 29x10^-6 g = 2.9x10^-5 g

2.9x10^-5 g x 1 mol/58 g = 0.05x10^-5 moles = 5x10^-7 moles (answer a)