Question

The hydrogen gas produced is collected over water at 25.0 oC. The volume of the gas is 7.80 L, and the total pressure in the gas collection vessel is 0.980 atm. Calculate the mass of zinc metal that reacted in grams.

Answer 1

Answer:

20.4 grams Zn

Explanation:

To find the mass, you first need to find the moles. This can be found using the Ideal Gas Law equation:

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = moles

-----> R = Ideal Gas Constant (0.08206 atm*L/mol*K)

-----> T = temperature (K)

Before you can plug the values into the equation, you need to convert Celsius to Kelvin.

P = 0.980 atm                   R = 0.08206 atm*L/mol*K

V = 7.80 L                          T = 25.0 °C + 273.15 = 298.15 K

n = ? moles

PV = nRT

(0.980 atm)(7.80 L) = n(0.08206 atm*L/mol*K)(298.15 K)

7.644 = n(24.466)

0.312 moles = n

Now that you have the number of moles, you can convert it to grams using the atomic mass of zinc. The final answer should have 3 sig figs to match the sig figs in the given values.

Atomic Mass (Zn): 65.380 g/mol

0.312 moles Zn           65.380 grams
-------------------------  x  -------------------------  =  20.4 grams Zn
                                         1 mole