1) What is the pH of a solution containing 0.2 g/L sodium carbonate and 0.1 g/L sodium hydrogen carbonate? (Ka1 = 4.1 x 10^-7, Ka2 = 5.6 x 10^-11)

I know to use the henderson-hasselbach equation but I'm unsure of which Ka to use for my pKa. Any insight would be great. I would assume Ka1?

2) What is the standard enthalpy of a reaction for which the equilibrium constant increases by a factor of ten when the temperature is increased from 273 K to 298 K?

I know the equation is lnK2/K1 = -delta H/R (1/T2 - 1/T1). I'm just confused on the wording "increased by a factor of ten". Would I put something like 30 as my K2 and 20 as my K1? Or would I just do the natural log of 10?