A student performs an experiment to determine the volume of hydrogen gas produced when a given mass of magnesium reacts with excess HCl (aq), as represented by the net ionic equation below. The student begins with a 0.0360 g sample of pure magnesium and a solution of 2.0 M HCl (aq). (equation: Mg(s) + 2H+ (aq) --> Mg2+ (aq) + H2 (g))

a. Calculate the number of moles of HCl (aq) needed to react completely with the sample of magnesium.

b. Calculate the number of moles of HCl (aq) needed to react completely with the sample of magnesium.

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = = 298 k

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

according to reaction 3 moles no are reacting with 1 mol of ,then 0.49 mol of no will react with moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3