Aluminum reacts with excess hydrochloric acid to form aqueous aluminum chloride and 46.5 mL of hydrogen gas over water at 27 degrees Celsius and 751 mmHg. How many grams of aluminum reacted? The partial pressure of water at 27 C is 26.8 mmHg.

Question

Ellie Andrews · Accepted Answer

#0.0324# #"g Al"#

We're asked to find the number of grams of #"Al"# that reacted, given some #"H"_2 (g)# product characteristics.

First, let's write this reaction's chemical equation:

#2"Al"(s) + 6"HCl"(aq) rarr2 "AlCl"_3(aq) + 3"H"_2 (g)#

The total pressure of the gaseous system is given as #751# #"mm Hg"#, and the partial pressure of water vapor is #26.8# #"mm Hg"# at #27^"o""C"#. The pressure of hydrogen gas is thus

#P_"total" = P_ ("H"_2"O") + P_ ("H"_2)#

#P_ ("H"_2) = 751# #"mm Hg"# #- 26.8# #"mm Hg"# #= color(red)(724# #color(red)("mm Hg"#

The atmosphere's pressure is

#724cancel("mm Hg")((1color(white)(l)"atm")/(760cancel("mm Hg"))) = color(red)(0.953# #color(red)("atm"#

We'll now use the ideal gas equation to find the number of moles of #"H"_2# formed:

(#T = 27^"o""C" + 273 = 300# #"K"#)

#n = (PV)/(RT) = ((color(red)(0.953)cancel(color(red)("atm")))(0.0465cancel("L")))/((0.082057(cancel("L")•cancel("atm"))/("mol"•cancel("K")))(300cancel("K"))) = color(green)(0.00180# #color(green)("mol H"_2#

(this volume is converted to liters)

Using the coefficients of the chemical equation, we'll now find the relative number of moles of #"Al"# that react:

#color(green)(0.00180)cancel(color(green)("mol H"_2))((2color(white)(l)"mol Al")/(3cancel("mol H"_2))) = color(purple)(0.00120# #color(purple)("mol Al"#

Lastly, we'll use the molar mass of aluminum (#26.98# #"g/mol"#) to find the number of grams that reacted:

#color(purple)(0.00120)cancel(color(purple)("mol Al"))((26.98color(white)(l)"g Al")/(1cancel("mol Al"))) = color(blue)(0.0324# #color(blue)("g Al"#

Thus, #color(blue)(0.0324# #sfcolor(blue)("grams of aluminum"# reacted.

Henry Antrim · Answer

undefined 2.73 grams of aluminum reacted.