Calculate the H positive from the pH equation: pH equals -log (H positive). This would be 10 to the -6.49. Let's call the acid HA. To calculate Ka in this equation, Ka equals H positive times A- over HA. HA is going to be the 0 0121. So, Ka=(10^-6.49)^2/0.0121. This equals 1.05*10^-13/0.0121. Ka then equals 8.65*10^-12.
Answer is: mass od zinc is 392,28 g.
N(Zn) = 3,6·10²⁴.
n(Zn) = N(Zn) ÷ Na.
n(Zn) = 3,6·10²⁴ ÷ 6·10²³ 1/mol.
n(Zn) = 6 mol.
m(Zn) = n(Zn) · M(Zn).
m(Zn) = 6 mol · 65,38 g/mol.
m(Zn) = 392,28 g.
Na - Avogadro number.
n - amount of substance.
M - molar mass.