Under SATP, magnesium was reacted with acid and 500mL of hydrogen gas was collected over water
a) What is the vapour pressure of water?
b) What is the pressure of hydrogen gas?
c) What amount of hydrogen was produced?
look up the vapor pressure of H2O at SATP. SUbtract that from SP, that is H2 pressure.
Now, knowing H2 pressure in the jar, and volume, and temp, calculate the moles of H2 collected (PV=nRT)
a. Don't you have a table in the book (or look it up on the web) to find the vapor pressure.
b. Ptotal = pH2 + pH2O. Ptotal is 1 atm and you know pH2O, solve for pH2.
c. Use PV = nRT. P from above, V is given, you know R and T is 25C (converted to K).
Post your work if you get stuck.
This is my answer below, it is close to the texbook answer but not exact.
a) V pressure of H2O = 25 degrees celcuis
= 3.17kPa H2O
(This was in my texbook by the way, I just didn't see it)
b) Pt=pH2+pH2O pt= 1 atm= 101.3kPa
101.3kPa =pH2 + 3.17kPa
101.3kPa - 3.17kPa = pH2
pH2= 98.13kPa (The textbook is 96.8kPa)
c) PV= nRT
98.13(0.55l) divided by 8.314kpa.l/mol.K = 0.0217
n= 0.0217
I would have worked the problem almost the same except I would have used101.325 since you used 3.17 which gives a slightly different answer of 98.15. That will change the moles slightly, too. However, I think I know how the book obtained 96.8 kPa. Standard pressure is often used as 1 bar or 100 kPa and 100-3.17 = 96.8 kPa.
I agree with DrBob. When the SATP was being debated, standard pressure was often debated to be 100kPa as "convenient"
To answer these questions, we need to understand the properties of water vapor pressure, the gas laws, and stoichiometry. Let's tackle each question step by step:
a) What is the vapor pressure of water?
The vapor pressure of water can be determined using a reference table or by using the Antoine equation. The vapor pressure of water is dependent on the temperature. Assuming we are at standard temperature and pressure (SATP), the vapor pressure of water is 1 atmosphere (atm) or 101.325 kilopascals (kPa).
b) What is the pressure of hydrogen gas?
To find the pressure of hydrogen gas, we need to consider the total pressure in the gas mixture. In this case, the hydrogen gas is collected over water, which means that the pressure consists of two components: the pressure exerted by hydrogen gas and the vapor pressure of water.
To calculate the pressure of hydrogen gas, we need to subtract the vapor pressure of water from the total pressure. Since we are given the total volume of hydrogen gas collected, we can assume that the gas inside the collection vessel is saturated with water vapor.
To find the partial pressure of hydrogen gas, subtract the vapor pressure of water from the total pressure (which is the atmospheric pressure):
Pressure of Hydrogen = Total Pressure - Vapor Pressure of Water
c) What amount of hydrogen was produced?
To determine the amount of hydrogen gas produced, we need to use stoichiometry, which relates the amount of reactants to the amount of products in a chemical reaction.
First, we need to know the balanced chemical equation for the reaction between magnesium and acid. Let's assume it is:
Mg + 2HCl → MgCl2 + H2
From the equation, we see that 1 mole of magnesium (Mg) reacts to produce 1 mole of hydrogen gas (H2).
Knowing the volume of hydrogen gas collected and the ideal gas law (PV = nRT), we can calculate the number of moles of hydrogen gas produced.
n = (PV) / (RT)
where:
P = pressure of hydrogen gas
V = volume of hydrogen gas collected
n = moles of hydrogen gas
R = ideal gas constant
T = temperature in Kelvin
By substituting the values into the equation, we can find the number of moles of hydrogen gas produced.
Please provide the additional information, such as the temperature and the concentration of the acid used, in order to proceed with the calculations.