Stoichiometry
Write the equation for the combustion of methanol, CH3OH (l). What mass of methanol is combusted in a reaction that produces 5 mol of CO2 gas?
160 g
A metallic cylinder contains 0.01765 mole H2S gas. The pressure in the cylinder is 725 mm Hg and the temperature is 23. oC. An additional 0.00125 mole of H2S is added into the cylinder. The temperature rises to 35. oC. Calculate the new pressure.
1.1 atm
Suppose 3260 J are absorbed by 135 g of water. If the initial temperature is 21.4 ̊C, what is the final temperature?
Tf = 27.2 ̊C
80.0 g KClO3 are mixed with 59.5 g HCl and allowed to react according to the equation: 2 KClO3 + 4 HCl → 2 KCl + 2 ClO3 + Cl2 + 2 H2O ( Molar mass: KCl = 74.6, KClO3 = 122.6, HCl = 36.5, ClO2= 67.5, Cl2 = 71.0, H2O = 18.0 g/mole) The amount of Cl2 produced is 18.7 g. Calculate the percent yield of Cl2.
(18.7 g Cl2)/(23.2 g Cl2) * 100% = 80.6%
The complete combustion of 0.430g of a gaseous compound that contains only C and H produced 672 ml of CO2 (g) measured at STP and 0.630 g of water. The 0.430 g sample occupied 156 ml at 50.0 oC and 0.850 atm. What is the empirical and molecular formula of the compound?
C3H7, C6H14
A sample of argon effuses through a tiny pinhole in 36.3 seconds. The same volume of an unknown gas effuses through the same pinhole in 65.2 seconds. What is the molar mass of the unknown gas?
129 g/mol
Calculate the quantity of heat, in kilojoules, that is associated with 4.9 L of water, decreasing in temperature from 42.0°C to 33.0°C.
qwater = -184514 J = -185 kJ
Aqueous mercury (I) acetate and aqueous cadmium iodide are mixed. Write the balanced chemical equation..
Hg₂(C₂H₃O₂)₂(aq) + CdI₂(aq) ---> Hg₂I₂ (aq) + Cd(C₂H₃O₂)₂ (aq)
Determine the number of moles and the mass (in kg) of copper(II) carbonate needed to decompose in order to produce 1.500 kg of copper(II) oxide, where CO2 is the other product. Write the balanced equation.
2CuCO3 (s) ---> 2CuO (s) + CO2 (g)
18.87 mol CuCO3
2.330 kg CuCO3
Automotive air bags inflate when a sample of sodium azide, NaN3, is very rapidly decomposed. What mass of sodium azide is required to produce 2.6 ft3 (73.6 L) of nitrogen gas with a density of 1.25 g/L?
142g NaN3
What are thermodynamic standard state conditions? How is this different from STP?
Thermo: 1 atm, 25 ̊C
STP (gases): 1 atm, 0 ̊C
Write the balanced equation for the combustion of octane, C8H18 (l).
2C8H18 (l) + 25O2 (g) ---> 16CO2 (g) + 18H2O (g)
What volume of 0.120 M NaOH solution is required to react completely with 40.0 mL of 0.200M H2SO4 solution? [Write the chemical equation first.]
133 mL
A compact car gets 37.5 miles per gallon on the highway. If gasoline contains 84.2% carbon by mass and has a density of 0.8205 g/mL, determine the mass of carbon dioxide produced during a 500-mile trip (3.785 liters per gallon).
1.28 × 105 g CO2
A large flask, of unknown volume, is filled with air until the pressure reached 3.60 atm. The flask is then attached to a second evacuated flask of 5.21 L volume, and the air from the first flask is allowed to expand into the second flask. The final pressure of the air in both flasks is 2.60 atm. Calculate the volume, in liters, of the first flask.
13.5 L
Calculate the quantity of heat, in kilojoules, that is required to raise the temperature of a 3.82 kg lead bar by 51.2°C (specific heat of lead = 0.128 J / g °C).
qlead = 25034.752 J = 25.03 kJ
Write the balanced equation for sulfuric acid and magnesium carbonate.
MgCO₃(s) + H₂SO₄(aq) → MgSO₄(aq) + CO₂(g) + H₂O(l)
What is a real gas? What is an ideal gas? Give two examples of non-ideality of gases and under what conditions they occur. Explain thoroughly and clearly what assumption(s) of kinetic molecular theory fail and how the ideal gas law fails to describe the behavior of the real gas. (Explain with complete sentences).
High Pressure: Gases will be compressed enough for the actual gas molecules to take up space (volume). Volume is no longer negligible. Volume is underestimated by the ideal gas law.
Low Temperature: Gas molecules move so slowly that they interact with each other through intermolecular forces (molecules are pulled towards each other, collisions are less elastic, molecules hit container walls with less force). Pressure is overestimated by the ideal gas law.
A 300 g sample of lead is heated in boiling water (100°C). The lead is then dropped inside a calorimeter with 100 g of water with an initial temperature of 22.0°C The final temp was observed to be 28.8°C. What is the specific heat of lead?
qH2O = 2842.4 J
qPb = -2842.4 J
cPb = 133 J/g°C