General Chemistry Review

Flashcards covering stoichiometry, gas laws, solutions, and molecular geometry.

What are the three subatomic particles that make up an ion, and how do their quantities differ from those in a neutral atom?

Protons, electrons, and neutrons; ions have an unequal number of protons and electrons compared to a neutral atom.

Which number on the left side of an element's symbol represents protons?

The smaller of the two numbers, also known as the atomic number.

How do you calculate the number of neutrons in an atom or ion?

Mass number minus the atomic number.

How do you determine the number of electrons in an ion?

Atomic number minus the charge of the ion.

If an ion has a +3 charge and 13 protons, how many electrons does it have?

10 electrons.

What type of compound is N2O5, ionic or molecular?

Molecular compound.

What characterizes a molecular compound?

Composed of nonmetals.

What type of compound is aluminum chloride (AlCl3), ionic or molecular?

Ionic compound.

What characterizes an ionic compound?

Between a metal and a nonmetal.

What naming conventions are used for molecular compounds like N2O5?

Prefixes like mono, di, tri, tetra, penta, etc.

What is the correct name for N2O5?

Dinitrogen pentoxide.

For ionic compounds like AlCl3, do you use prefixes in the name?

No, you just name it aluminum chloride.

How would you name the compound SF6?

Sulfur hexafluoride.

Is MgF2 an ionic or molecular compound, and what is its correct name?

Ionic compound; magnesium fluoride.

What is the formula for calculating the percent composition of an element in a compound?

(Mass of element / Total mass of compound) * 100%

If the molar mass is used when calculating percent composition, will you get a different answer?

No.

What is the percent composition of aluminum in aluminum sulfide Al2(SO4)3?

18.37%.

Why is it crucial to write a balanced chemical equation when performing stoichiometric calculations?

To determine the correct molar ratios between reactants and products.

What are the diatomic elements?

N2, H2, O2, F2, Cl2, Br2, I2.

What is the limiting reactant in a chemical reaction?

The reactant that runs out first, determining the maximum amount of product that can be formed.

List the four general steps for doing a gram to gram conversion using stoichiometry

1. Convert grams of reactant A to moles. 2. Convert moles of reactant A to moles of substance B using the coefficients in the balanced equation. 3. Convert moles of substance B to grams.

In the reaction N2 + 3H2 -> 2NH3, if you start with 15 grams of N2, how many grams of NH3 are produced?

18.24 grams of NH3.

What is molarity defined as?

Moles of solute divided by liters of solution.

What is the chemical formula for sodium hydroxide?

NaOH.

How do you convert milliliters to liters?

Divide by 1000.

If 15 grams of NaOH is dissolved in enough water to produce 250 mL of solution, what is the molarity?

1.5 M.

What is another way to calcuate molarity other than through dimensional analysis

Use the formulas: mass = moles x molar mass and molarity = moles / volume in liters.

What equation is used for dilution problems?

M1V1 = M2V2

If you dilute 200 mL of a 0.75 M solution to a concentration of 0.25 M, what is the final volume?

600 mL.

If you dilute 200 mL of a 0.75 M solution to get a solution with a concentration of 0.25 M, how much water did you add?

400 mL.

What is oxidation state?

A number assigned to an element in a chemical combination that represents the number of electrons lost or gained

What is the sum of the oxidation states of all the atoms in a neutral compound?

Zero.

What is the sum of the oxidation states of all the atoms in a polyatomic ion?

Equal to the charge of the ion.

What is the most common oxidation state of oxygen?

–2

What is the common oxidation state of hydrogen?

+1 when bonded to a nonmetal, -1 when bonded to a metal.

What is the oxidation state of chromium in sodium dichromate (Na2Cr2O7)?

+6.

What is the oxidation state of hydrogen in calcium hydride (CaH2)?

-1.

What are some elements that have an oxidation state of zero?

H2, N2, O2

What is the oxidation state of oxygen in peroxides?

-1.

What is the oxidation state of fluorine in a compound?

–1

What equation do you use for titrations?

M1V1 = M2V2

When using the M1V1=M2V2 equation, what must you take into account when there are two different substances?

The molar ratio in the chemical equation. You must incorporate the molar ratio

What is the molarity of a sulfuric acid solution (H2SO4) if 38.6 mL of 0.249 M NaOH is required to completely titrate 44.7 mL of the acid?

0.108 M.

In dimensional analysis for titrations, should you begin with the compound you are solving for?

No.

What is the combined gas law?

P1V1/T1 = P2V2/T2

What units must the temperature be in when using the combined gas law?

Kelvin.

A 250 mL sample of argon gas has a pressure of 1.25 atm at 300 K. What is the new pressure if the temperature is increased to 500 K and the volume is decreased to 100 mL?

5.21 atm.

What does STP stand for?

Standard Temperature and Pressure.

What are the values for temperature and pressure at STP?

0 degrees Celsius (273 K) and 1 atm.

what is the volume that is occupied at one mole of any gas at STP?

22.4 Liters

What two values do you need to know to calculate the density of a gas at STP?

The molar mass and ideal volume.

What is the density of oxygen gas (O2) at STP?

1.43 g/L.

What is the equation for the density of a gas?

Density = (Pressure * Molar Mass) / (R * T)

What is the Ideal Gas Law?

PV = nRT

What is the value of R (gas constant) most commonly used in the ideal gas law when pressure is in atmospheres?

0.08206 Latm/molK

What is partial pressure?

The contribution each gas in a mixture makes to the total pressure

How do you find the partial pressure of a gas?

Use the ideal gas Law.

How do you balance the equation for partial pressures with vapor pressure?

Partial pressure of gas + partial pressure of water = total pressure

What is the partial pressure of ammonia (NH3) if 24 grams of nitrogen gas (N2) reacts with excess hydrogen gas at 298 K inside a 2.5 L container?

16.8 atm.

4. 722 grams of an unknown gas is collected over water inside a 2.75 liter container at 298 Kelvin and the total pressure inside the container is 749 Torr and the vapor pressure of water is 23.76 Torr. What are your first steps to determine the molar mass?

Need to subtract vapor pressure of water from the total.

4. 722 grams of an unknown gas is collected over water inside a 2.75 liter container at 298 Kelvin. After the vapor pressure of water is subtracted, the pressure is 725.24 torr, what is the aTm?

0.9542 atm

When finding the identity of an unknown gas what must you find in comparison to answer choices

Calculate by molar mass and then you want to find the molar mass of every answer choice.

4. 722 grams of an unknown gas is collected over water inside a 2.75 liter container at 298 Kelvin. The total pressure inside the container is 749 Torr, and the vapor pressure of water is 23.76 Torr. What is the identity of the unknown gas?

Carbon dioxide.

What is the total pressure exerted by a mixture of gases equal to?

The sum of the partial pressures of each individual gas.

Which of the following statements is not correct: a) The average kinetic energy of a sample of gas is dependent on temperature; b) The pressure inside a container is dependent on the total number of moles of gas; c) Heavier gas particles exert a greater pressure on the walls inside of the container; d) The average velocity of gas particles is dependent on temperature.

c) Heavier gas particles exert a greater pressure on the walls inside of the container.

Which conditions allow a real gas to behave more like an ideal gas?

High temperature and low pressure.

Which way does low pressure favour the formation of.

Formation of gas

What equation do you use to calculate the energy required to heat a substance?

Q = mcΔT

If 75 grams of water is heated from 25°C to 74°C, how much energy is required (specific heat capacity of water = 4.184 J/g°C)?

15.4 kJ.

What equation to you use when you have face charges?

Q + moles x H fusion (kilojoules per mole) or mass x enthalpy of fusion (joules per gram)

How much heat energy is required to melt 25 grams of ice (heat of fusion = 6.01 kJ/mol)?

8.347 kJ.

As you go from a solid to a liquid it's called melting, is an endothermic or exothermic process?

Endothermic.

Reverse is true if you want to freeze liquid water into ice you has to remove or add heat?

Remove heat. This is an exothermic process

What is a phase change from a gas to solid called?

Deposition.

What phase change is from a solid to a liquid?

Melting

What phase change is from a liquid to gas?

Vaporization.

What phase change is from a solid to a gas?

Sublimation.

What phase change is from a liquid to a solid?

Freezing.

What phase change is from a gas to a liquid called?

Condensation

How can the enthalpy of a reaction be calculated?

ΔH = Σ(Enthalpies of Products) - Σ(Enthalpies of Reactants)

What values do you exclude when calculating the enthalpy of a reaction equation?

Elements in their purest form.

What is the enthalpy of combustion of ethanol (C2H5OH) given certain values?

-1367.7 kJ/mol.

Where do you get this molar mass number from in the balance equation?

This equation can be used to convert the mass, moles and kilojoules

How can energy in kilojoules be calculated from thermochemical equations?

Convert grams to moles, then moles to kilojoules using the balanced equation.

How much heat energy is released if 10.5 grams of propane (C3H8) reacts with excess oxygen?

525 kJ.

What is Planck's equation?

E=hv, E=hc/wavelength

How can the energy of a photon be found from wavelength?

E = h * c / wavelength

What is the energy of a photon that has a wavelength of 451 nm?

4.408 x 10^-19 J.

What is the quickest way to to find if there is the right answer, when you have a multiple choice?

Use the atomic number

What is the ground state electron configuration for fluorine?

1s2 2s2 2p5.

What number do electron configuration exons have to add up when given the atomic number?

They must add up to 28 for nickel

What number is represented by 'n'?

The three n is three in all these levels.

What is the numerical value for the s sublevel?

0.

What is the numerical value for the p sublevel?

1.

What is the numerical value for the d sublevel?

2.

What is the numerical value for the f sublevel?

3.

Which four quantum numbers correspond to the last electron found in nickel?

n=3, l=2, ml=0, ms=-1/2.

What is the formula to remember sub levels in quantum numbers?

SPDF 0123.

When looking for the spin to solve quantum numbers, is downward electrons a positive or negative number?

Negative.

What are quick things to remember, when trying to find all of four set values in quantum numbers?

compare n and l. Has to at least be n-1, has to find L with the ML values or orbitals.