Answer
Element X is Se or selenium
Hydroselenic acid would be the name
0.252 g of $H_2Se$ used
Work Step by Step
Since element $X^{2-}$ has 36 electrons, we know that element X has 34 electrons normally when it has no charge. Hence, the element has 34 protons, which is Selenium. Since $H_2Se$ is a binary acid, we would name it hydroselenic acid. By balancing the equation given in the problem, we know that we need 2 moles of hydroxide ions for 1 mole of acid. To calculate the total moles of hydroxide ions, we multiply the concentration of it by the number of liters used. This gives us $0.175\times 0.0356$, which is 0.00623 moles of hydroxide. We divide this number by 2 to find the moles of acid which gives 0.003115 moles of acid. Multiplying the number of moles of hydroselenic acid by its molar mass, $80.976$, we obtain a total mass of 0.252 g of $H_2Se$.