Moles, Chemical Bonding, and Stoichiometry
At the atomic level, describe the differences between a molecular compound and an ionic compound.
Molecular compounds share electrons (like water, H2O), while ionic compounds transfer electrons (like table salt, NaCl)
What are STP conditions? How does this relate to molar volume?
What are thermodynamic standard state conditions? How is this different from STP?
Thermo: 1 atm, 25 ̊C
STP (gases): 1 atm, 0 ̊C
What indicators allow you to deduce if a molecular compound is an acid?
Acids typically contain hydrogen and release H⁺ ions in solution; they often start with "H" in their formula, such as HCl or H₂SO₄.
Write down a conversion factor for 1) Nitrogen and 2) HCl that uses Avogadro's number.
(Remember: When you do dimensional analysis, you apply Avogadro's number to your calculation using a fraction with numbers and units. This fraction is called a conversion factor.)
1) 1 mol N / 6.022 x 1023 atoms N
2) 1 mol HCl / 6/022 x 1023 molecules HCl
What is an ideal gas, and how does it differ from a real gas?
An ideal gas follows gas laws perfectly because its particles have no volume, no IMF, and collisions between particles are perfectly elastic. PV=nRT works. In real gases, their gas particles can interact with each other and take up space (volume is no longer negligible). PV=nRT does not work for real gases without adjustment.
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
Give the chemical formula for
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
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
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
Using Hess’s Law, calculate the enthalpy (ΔHrxn) of this reaction: CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g)
[3 C (s) + 6 H2 (g) → 3 CH4 (g) ; ΔHf = -112.60 kJ/mol]
[C (s) + O2 (g) → CO2 (g) ; ΔHf = -525.09 kJ/mol]
[H2O (g) → H2 (g) + ½ O2 (g) ; ΔHf = +379.45 kJ/mol]
ΔHrxn = -1246.46 kJ/mol
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
The density of a 0.323 M aqueous solution of sodium phosphate (Na3PO4, MM 163.94 g/mol) is 1.048 g/mL. Calculate the molality and percent by mass of the solution.
0.325 m Na3PO4
5.052% Na3PO4
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 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