What is the [H+] concentration of a solution whose pOH is 12.40?

A5.000 g sample of niso4 h2o decomposed to give 2.755 g of anhydrous niso4. what is the formula of the hydrate? what is the full chemical name for the hydrate? what is the molar mass of the hydrate? niso4•_h2o what is the mass % of water in the hydrate?

Chemistry worksheet - i am not sure what they are asking for exactly?

Draw the aromatic compound toluene (methylbenzene). show all hydrogen atoms, including those on the ring.