19.80cm³ of a solution containing 1.15g of Hydrogen chloride on 250cm³ netralized 25cm³ of an unknown trioxocarbonate(IV) acid salt, X2CO3 have a concentration of 5.30gdm³, Calculate Concentration of X2CO3 in molesdm³

The reactions shown here can be combined to make the overall reaction c(s) + h2o(g) ⇌ co(g) + h2(g) by reversing some and/or dividing all the coefficients by a number. a. c(s) + o2(g) → co2(g) k=1.363×10^69 b. 2 h2(g) + o2(g) → 2 h2o(g) k=1.389×10^80 c. 2co(g) + o2 (g) → 2 co2(g) k=1.477×10^90

What metric units would you use to measure the thickness of a key

Iwould appreciate if someone could me.