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 = 
Formula weight of NaHCO₃ = 
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 = 
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%
you add all the letters together
Answer:
The answer is in the explanation.
Explanation:
A buffer is defined as the aqueous mixture of a weak acid and its conjugate base or vice versa. Buffers are able to avoid the pH change of a solution when strong acid or bases are added (As NaOH).
Based on the experiment, it is possible that the solution Z was a buffer and Y another kind of solution. For this reson, pH of the solution Y changes much more than the pH of solution Z changes despite the amount of NaOH added is the same in both solutions.