First you divide the given mass of A (the initial substance) by its molar mass to get its number of moles. Then, based on a balanced chemical reaction, you divide the number of moles by the coefficient of A, then multiply by the coefficient of the product B. Finally, multiply by the molar mass of the product B (if there is a given conversion or yield %, multiply it as well), and this gives the amount of grams of the product.
The answer is b. 4.2 mole. The balanced reaction formula is 2LiOH + H2SO4 -->Li2SO4 + 2H2O. And the ratio of mole number of the reactants is the same as the ratio of coefficients.
The answer is common table salt. Looking at the chemical make up, putting an acid (I think chlorine) and and base (probably sodium) makes water (H20) and salt. So you answer would be salt