please help me with these homework problems from chemistry because the teacher did not give enough information to some of these chemistry work problems.
1) 50.0 g of aluminum is reacted with excess sulfuric acid. The chemical equation for the reaction is:
2Al + 3H2SO4 --> Al2(SO4)3 + 3H2
If 58.7 L of H2 are collected over water at 20 degree C and 785 torr, what is the mass percent yield?
(Vapor pressure of water at 20 degree C is 17.5 torr.)
2) What is the density of hydrogen, in g/L, under lab conditions? Under STP conditions?
3) Carbon monoxide can be reacted with hydrogen to produce methanol. The chemical equation for the reactions is:
CO(g) + 2H2 --> CH3OH(g)
If 52.10 L of hydrogen gas at STP is completely reacted with excess carbon monoxide gas,what volume in liters of methanol st STP will be produced?
4) The 4.25 grams of sugar (C6H12O6) reacts with sufficient oxygen to produce 3340 mL of carbon dioxide collected over water at 751.9 mm Hg at 24 degree C. Vapor pressure of water at 24 degree C is 22.4 mm Hg. What is the percent yield?
I am giving outlines below for solving problems #1 and #2. The others involve the same or similar principles. The general topic is reaction stoichiometry. It is hard to cover such a broad topic adequately through postings here.
Question #1
(a) Use the Ideal Gas Law to find the moles of H2
PV = nRT
P = (785 torr - 17.5 torr)/760 torr/atm = _____ atm
V = given
R = 0.0821 L.atm/K.mol
T = 20.0 + 273 = _____K
*n = (Solve for this variable)
(b) The % yield must be based on the limiting reagent.
Convert 50.0g of Al to moles (divide by 27.0 g/mol)
The mole ratio of H2 to Al is 3/2 = 1.5 according to the chemical equation.
(moles Al)(1.5) = Theoretica l Yield of H2
% yield = [calculated moles H2 / Theoretical yield](100)
Question 2
(a) Density at existing temperature:
Assume you have 1.00 mole of H2 = n
Using the Ideal Gas Law, substitute P = (pressure in atm. you calculated earlier), V = (unknown to solve for), n = 1, R = 0.0821 L.atm/K.mol, T = 293 K. Solve for V (volume in liters). Divide the molar mass of H2 by the calculated volume for 1 mole.
(b) Density at STP:
Divide the molar mass of H2 by 22.4 L.
Certainly! I'd be happy to help you with your chemistry homework problems.
Before we proceed with the specific questions, it's important to understand the steps involved in solving these chemical problems. Here's a general approach you can follow:
1) Write and balance the chemical equation for the given reaction.
2) Convert the given information into the appropriate units if needed.
3) Determine the limiting reactant (if necessary).
4) Calculate the amount of the desired product using stoichiometry.
5) Convert the answer to the desired units or form (e.g., mass percent yield or volume at STP).
6) Finally, if applicable, compare the calculated value with the theoretical or expected value to calculate the percent yield.
Now, let's apply this approach to solve the individual problems you mentioned:
1) Mass Percent Yield:
a) First, calculate the moles of hydrogen gas collected at 20 degrees Celsius and 785 torr.
- Use the Ideal Gas Law: PV = nRT, where P = 785 torr, V = 58.7 L, and T = 20°C (convert to Kelvin).
- Rearrange the formula to solve for n (moles).
- Remember to subtract the vapor pressure of water (17.5 torr) from the total pressure.
b) Using the balanced chemical equation, determine the theoretical yield of hydrogen gas in moles.
c) Now, calculate the mass of the theoretical yield of hydrogen gas using the molar mass of H2.
d) Finally, use the actual yield of hydrogen gas (mass) and the calculated theoretical yield (mass) to determine the mass percent yield using the formula: (actual yield / theoretical yield) x 100%.
2) Density of Hydrogen:
a) Under lab conditions:
- Use the molar mass of hydrogen (H2) and the Ideal Gas Law to calculate the density of hydrogen gas (g/L) at the given lab conditions.
b) Under STP conditions:
- STP (Standard Temperature and Pressure) refers to 0°C and 1 atm pressure.
- Consequently, the density of hydrogen gas (g/L) under STP conditions can be calculated similarly using the molar mass and the Ideal Gas Law.
3) Volume of Methanol at STP:
a) Use the given volume of hydrogen gas at STP (52.10 L) and the balanced chemical equation to determine the stoichiometric ratio between hydrogen and methanol.
b) Calculate the volume of methanol gas formed at STP using the stoichiometric ratio.
4) Percent Yield Calculation:
a) Start by calculating the moles of carbon dioxide produced using the ideal gas law.
- Utilize the given volume of carbon dioxide (3340 mL), the temperature (24°C), and the total pressure (751.9 mm Hg, subtracting the vapor pressure of water).
b) Convert the moles of carbon dioxide to moles of sugar (C6H12O6) using the balanced chemical equation.
c) Calculate the theoretical yield of sugar (C6H12O6) in grams using the molar mass of sugar.
d) Finally, calculate the percent yield using the actual yield (mass of sugar) and the theoretical yield (mass of sugar), following the formula: (actual yield / theoretical yield) x 100%.
Please follow these steps and if you have any specific questions about a particular problem, I will be glad to assist you further.