Question #ded6c

Find the percentage mass of each element of salt, sodium chloride (NaCl)

Sodium = 23.0 grams ( to three significant digits)
Chlorine= 35.5 grams ( to three significant digits.)

The molar mass of Sodium Chloride is
# 23.0 + 35.5 = 58.5# grams

The mass percent of sodium is

# 23.0/58.5 = 39.3#%

# 39.3% xx 47 .0 g = 18.5 g#

The mass percent of Chlorine is

# 35.5/58.5 = 60.7#%

# 60.7% xx 47.0g = 28.5 g#

Here's another way to do the calculation.

Start with the balanced equation:

#M_text(r): color(white)(ll)22.99color(white)(m)70.91color(white)(mll)58.44#
#color(white)(mmm)"2Na" + color(white)(l)"Cl"_2 → "2NaCl"#

Calculate the mass of #"Na"#

#"Moles of NaCl" = 47.0 color(red)(cancel(color(black)("g NaCl"))) × "1 mol NaCl"/(58.44 color(red)(cancel(color(black)("g NaCl")))) = "0.8042 mol NaCl"#

#"Moles of Na" = 0.8042 color(red)(cancel(color(black)("mol NaCl"))) × "2 mol Na"/(2 color(red)(cancel(color(black)("mol NaCl")))) = "0.8042 mol Na"#

#"Mass of Na" = 0.8042 color(red)(cancel(color(black)("mol Na"))) × "22.99 g Na"/(1 color(red)(cancel(color(black)("mol Na")))) = "18.5 g Na"#

Calculate the mass of #"Cl"_2#

#"Moles of Cl"_2 = 0.8042 color(red)(cancel(color(black)("mol NaCl"))) × "1 mol Cl"_2/(2 color(red)(cancel(color(black)("mol NaCl")))) = "0.4021 mol Na"#

#"Mass of Cl"_2 = 0.4021 color(red)(cancel(color(black)("mol Cl"_2))) × "70.91 g Cl"_2/(1 color(red)(cancel(color(black)("mol Cl"_2)))) = "28.5 g Na"#