This is a stoichiometry problem, where we have an initial amount of reactant and we need to find out how much of the product will we end up with, in order to do that we need to:
1. Set up the properly balanced equation, which the question already provided us
Zn + 2 HCl -> H2 + ZnCl2
2. See how many moles of reactant there are in the given amount of grams, using its molar mass, 65.38g/mol, and the given mass in the question, 0.238 grams:
65.38g = 1 mol of Zn
0.238g = x moles of Zn
65.38x = 0.238
x = 0.238/65.38
x = 0.00364 moles of Zn
3. Check the molar ratio between the two compounds, which we can determine by the balanced equation, the molar ratio will be 1 to 1, therefore if we have 0.00364 moles of Zn, we will also have 0.00364 moles of ZnCl2
4. Calculate how many grams will be equal to the number of moles that we found out, 0.00364 moles, using the molar mass, 136.286g/mol
136.286g = 1 mol
x grams = 0.00364 moles of ZnCl2
x = 0.00364 * 136.286
x = 0.496 grams of ZnCl2 will be produced from 0.238 grams of Zn