Question

What is the percentage by mass of oxygen in a formula unit of sodium hydrogen carbonate (NaHCO3)?

Answer 1

((8×3)÷(11+1+6+16+(8×3)))×100

Answer 2

Percent by mass of an element can be calculated as

(Total mass of the element in the formula / formula weight ) * 100

Step 1 : Find formula weight of NaHCO₃

To find formula weight of NaHCO₃, we have to add atomic masses of the elements Na, H,C and O

Formula weight of NaHCO₃ = $Na+H+C+3 (O)$

Formula weight of NaHCO₃ = $22.99+1.01+12.01+3(16)$

Formula weight of NaHCO₃ is 84.01 g

Step 2 : Use percent by mass formula

Percent by mass of oxygen = (total mass of oxygen / formula weight) * 100

Percent by mass of oxygen = $\frac{3(16)}{84.01} * 100$

Percent by mass of oxygen = 57.14%

Answer : percentage by mass of oxygen in a formula unit of sodium hydrogen carbonate (NaHCO3) is 57.14%