Question

1) in the lab, a 1.60 g sample of pure potassium metal enters 3.00 g of water. Using dimensional analysis set up ( stoichiometry), please calculates the limiting reagent as potassium hydroxide and hydrogen gas are produced. 2) you have 2.5 l of gas at 35 degrees c. What is the volume if you heat the sample to 130 degree c?the pressure is constant. 3) calculate the volume of hydrogen gas in a tank if 0.525 miles of the gas exert a pressure of 3.00 atm at 10.0 c.

Answer 1

1)

2 K (s) + 2 H2O (l)   -------------> 2 KOH (aq) + H2 (g)

78.2 g        36.04 g

1.60 g        3.00 g

78.2 g K -------------> 36.04 g H2O

1.60 g K   -------------> ??

mass of water needed = 1.60 x 36.04 / 78.2

                                   = 0.737 g

but we have 3.00 g of water .s o water is excess.

potassium metal (K) is limiting reagent.

2)

volume V1 = 2.5 L

temperature T1 = 35 oC = 308 K

T2 = 130 oC = 403 K

V1 / T1 = V2 / T2

2.5 / 308 = V2 / 403

V2 = 3.27

volume of gas = 3.27 L

3)

temperature = 20 oC = 283 K

pressure = 3.00 atm

moles = 0.525 mol

P V = n R T

3 x V = 0.525 x 0.0821 x 283

V = 4.07

volume of hydrogen gas = 4.07 L