Chlorine dioxide, ClO2, has been used as a disinfectant in air conditioning systems. It reacts with water according to the following equation. ... HCl If 142.0 g of ClO2 is mixed with 33.0 g of H2O, how many grams of which reactant remain if the reaction is complete?

Answer 1

Write the equation. You didn't complete it.
ClO2 + H2O ==>

Then balance the equation.
Convert 33.0 g H2O and 142.0 g ClO2 to moles. moles = grams/molar mass.

Using the coefficients in the balanced equation, convert moles of each to moles of product. The reactant producing the smaller number of moles of the product will be the limiting reagent. That will identify the limiting reagent, which by the way, will be used completely.
To determine how much of the OTHER reagent remains:
a. Convert moles of the limiting reagent to moles of the OTHER reagent using the coefficients in the balanced equation. This will be the moles of the other reagent used. Subtract the initial moles from the moles used to determine moles remaining. Then convert that to grams. g = moles x molar mass.
Post your work if you get stuck.