What is the component concentration ratio, [no2−]/[hno2], of a buffer that has a ph of 3.90? (ka of hno2 = 7.1 × 10−4)?

According to Henderson–Hasselbalch Equation,

                                    pH  =  pKa + log [Nitrate] / [Nitric Acid]

As,      Ka of Nitric Acid  =  7.1 × 10⁻⁴
So,
           pKa  =  -log [ 7.1 × 10⁻⁴ ]

           pKa  =  3.148

So,                               pH  =  3.148 + log [Nitrate] / [Nitric Acid]

                                  3.90  =  3.148 + log [Nitrate] / [Nitric Acid]

                      3.90 - 3.148  = log [Nitrate] / [Nitric Acid]

                                0.752  =  log [Nitrate] / [Nitric Acid]

Taking Antilog on both sides,

                                  [Nitrate] / [Nitric Acid]  =  5.64

Adozen is 12, and your needing to calculate the weight of one medium egg, so i would do 21/12=1.75 per egg, and check your answer by doing 1.75 * 12= 21 : ) : ): ): ): ) i hoped i