How many moles of potassium are in 0.256 g?

1 Answer
Mar 16, 2016

Answer:

#n~~0.00655mol#

Explanation:

Recall that the formula for moles is:

#color(blue)(|bar(ul(color(white)(a/a)n=m/Mcolor(white)(a/a)|)))#

where:
#color(magenta)n=#number of moles
#color(orange)m=#mass (grams)
#color(teal)M=#molar mass (grams/mole)

Since you already have the mass of potassium, #color(orange)(0.256g)#, and the molar mass, #color(teal)(39.1g/(mol))#, which can be determined by looking at a periodic table, the only variable left to solve for is #color(magenta)n#, the number of moles. Thus:

#color(magenta)n=color(orange)m/color(teal)M#

#color(magenta)n=color(orange)(0.256g)/color(teal)(39.1g/(mol))#

#n=0.256g*(mol)/(39.1g)#

#n=0.256color(red)cancelcolor(black)g*(mol)/(39.1color(red)cancelcolor(black)g)#

#n=0.006547314578mol#

#color(green)(|bar(ul(color(white)(a/a)n~~0.00655molcolor(white)(a/a)|)))rArr#rounded off to #3# significant figures