Simple chem wuestions on gas lwas: pressure, volume, etc and I rlly need help Please!!?

Question

Solid Zinc reacts with aqueous HCL to produce Zinc chloride and Hydrogen gas. In a rcent experiment, 20 grams of Zn reacted to produce H2 at 30 degreed C and at a pressure of 700 mm Hg.

1. Determine the volume of H2 collected at STP.
2. Calculate the pressure of the dry hydrogen gas.
3. calculate the volume of H2 collected at the conditions it was collected.
4. Determine the mass of hydrogen gas collected.
5. calculate the experimental density of H2 from the lab data.
6. calculate the accepted value for density of hydrogen gas
7. calculate the percent error.

PLEASE SHOW WORK!!!! thank you and for answers... best answer + 5 stars!!!! thanks again!

Answer 1

write equation & balance:

Zn + 2HCL ---> ZnCL2 + H2

T = 30 celcius + 273 = 303 K
P = 700 mm Hg ---> x
760 mm Hg ----> 101.3 kPa
x = 93.3 kPa

20 g of Zn / (65.41g/mol) = 0.3058 mol

use mol-mol ratio: 0.3058 x 2/1 = 0.6115 mol of H2

PV = nRT
(101.3)V = (0.6115)(8.314)(273)

V = 13.7 L of H2 gas at STP


2. Ptotal - P of water at 30 celcius (4.24 kPa) = PH2
93.3 - 4.24
P of H2 = 89.06 kPa


3.
PV = nRT
(93.3)V = (0.6115)(8.314)(303)
V = 16.5 L of H2 at collected conditions

4. 0.6115 mol x 2.02g/mol = 1.24 g of H2 collected

5. D = m/v
D = 1.24 / 16500
D = 0.000075 g/mL or 0.075 kg/L

6. don't know

7. % yeild = actual yeild/ theoretical yeild x 100

-i hope this helps, sorry i couldn't do the rest.
:)

Answer 2

Zn(s) + 2HCl(aq) ===> ZnCl2(aq) + H2(g)

Atomic weights: Zn=65.4 H=1 H2=2

1. 20gZn x 1molZn/65.4gZn x 1molH2/1molZn x 22.4LH2/1molH2 = 6.85 L H2 at STP

2. For this, you need to know the vapor pressure of water at 30C. Apparently, the H2 gas was collected over water. So the pressure of H2 is (700 - x), where x is the vapor pressure of water.

3. Assuming that the gas was NOT collected over water,

6.85LH2 x 760mmHg/700mmHg x 303K/273K = 8.25 L H2

4. 20gZn x 1molZn/65.4gZn x 1molH2/1molZn x 2gH2/1molH2 = 0.612g H2 collected, which does not depend on whether collected over water

The other answers to your question depend on the vapor pressure of water at 30C