Chapter 3 Flashcards
What is an aqueous solution?
Solution for which water is the solvent
Aqueous solutions are commonly used in chemistry as they involve water as the primary solvent.
What is Avogadro’s number (NA)?
Experimentally determined value of the number of entities comprising 1 mole of a substance, equal to 6.022 × 10^23 mol−1
Avogadro’s number is fundamental in converting between moles and particles.
What does the term concentrated refer to in a solution?
Qualitative term for a solution containing solute at a relatively high concentration
Concentrated solutions have a higher ratio of solute to solvent.
Define concentration in the context of solutions.
Quantitative measure of the relative amounts of solute and solvent present in a solution
Concentration can be expressed in various units, including molarity and percent by volume.
What does dilute mean when describing a solution?
Qualitative term for a solution containing solute at a relatively low concentration
Dilution results in a lower concentration of solute in the solution.
What is dilution?
The process of adding solvent to a solution in order to lower the concentration of solutes
Dilution is commonly performed in laboratory settings to achieve desired concentrations.
What does dissolved mean?
Describes the process by which solute components are dispersed in a solvent
Dissolution is essential for creating solutions where solutes are uniformly distributed.
What is the empirical formula mass?
Sum of average atomic masses for all atoms represented in an empirical formula
The empirical formula represents the simplest whole-number ratio of elements in a compound.
What is formula mass?
Sum of the average masses for all atoms represented in a chemical formula; for covalent compounds, this is also the molecular mass
Formula mass is used to calculate the mass of a specified amount of a substance.
Define mass percentage.
Ratio of solute-to-solution mass expressed as a percentage
Mass percentage is commonly used in chemistry to express the concentration of a solution.
What is mass-volume percent?
Ratio of solute mass to solution volume, expressed as a percentage
This measure is particularly useful in solutions where the volume is relevant for the solute’s concentration.
What is molar mass?
Mass in grams of 1 mole of a substance
Molar mass is essential for converting between grams and moles in stoichiometric calculations.
What does molarity (M) represent?
Unit of concentration, defined as the number of moles of solute dissolved in 1 liter of solution
Molarity is a crucial concept in preparing solutions and performing dilutions.
What is a mole?
Amount of substance containing the same number of atoms, molecules, ions, or other entities as the number of atoms in exactly 12 grams of 12C
The mole is a fundamental unit in chemistry for quantifying entities at the atomic or molecular level.
Define solute.
Solution component present in a concentration less than that of the solvent
Solutes can be solids, liquids, or gases that are dissolved in solvents.
Define solvent.
Solution component present in a concentration that is higher relative to other components
The solvent is often the major component of a solution and determines the phase of the solution.
What is volume percentage?
Ratio of solute-to-solution volume expressed as a percentage
Volume percentage is useful for expressing concentrations of liquids in solutions.
What is percent composition?
Percentage by mass of the various elements in a compound
Used to determine the contribution of each element to the total mass of the compound.
What does the formula for an ionic compound NOT represent?
The formula for an ionic compound does not represent the composition of a discrete molecule.
Why might the term ‘molecular mass’ be incorrectly used for ionic compounds?
Because the average masses of neutral atoms were used in computation, rather than the masses for cations and anions.
Fill in the blank: The formula for an ionic compound may not be correctly referred to as the _______.
[molecular mass]
What is the molecular mass (amu) for Acetaminophen C8H9NO2?
151.16 amu
What is the formula mass (amu) of Calcium phosphate Ca3(PO4)2?
310.18 amu
What unit is used to express formula mass?
amu
What is the atomic mass unit (amu) equivalent to?
Molar mass (g/mol)
The atomic mass unit is a standard unit of mass that quantifies mass on an atomic or molecular scale, equivalent to one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state.
What is the estimated average of 4.7g potassium in moles?
0.12 moles
Calculation: 4.7 g x (1 mol K / 39.1 g K) = 0.12 mol K
How many moles of Be are in a 3.24 g thin-foil window?
0.360 mol Be
3.24 g x (1 mol Be / 9.01 g Be) = 0.360 mol Be
How is the molar amount of a substance calculated?
By dividing its mass (g) by its molar mass (g/mol)
Molar amount is a key concept in chemistry for quantifying substances.
What is the sequence for converting units from mass to atoms?
mass (grams) –> moles –> atoms (molecules)
This sequence is essential for stoichiometric calculations in chemistry.
To convert mass (grams) to moles, what operation is performed?
Divide mass (grams) by molar mass (g/mol)
Molar mass is specific to each substance and is typically expressed in grams per mole.
How do you convert moles to atoms (molecules)?
Multiply moles by Avogadro’s number
Avogadro’s number is approximately (6.022 imes 10^{23}) particles per mole.
What is the mass of argon in a liter of air 9.2 x 10^-4 mol Ar?
0.04 g Ar
9.2 x 10^-4 mol Ar x (39.95 g Ar / 1 mol Ar) = 0.04 g Ar
This is calculated based on the molar mass of argon and the amount in moles.
What is the mass of 2.561 mol of gold?
504.4 g
How many grams of pure gold does the prospector collect?
15.00 g
Calculate the number of Au atoms in a quantity of gold that weighs 15.00 g. What is the result?
4.586 × 10^22 Au atoms
How many copper atoms are in 5.00 g of copper wire?
4.74 x 10^22 atoms Cu
5.00 g (1 mol / 63.55 g ) (6.022 x 10^23 atoms / 1 mol) = 4.74 x 10^22
How many moles of glycine molecules are contained in 28.35 g of glycine C2H5O2N?
0.378 mol glycine
28.35 g (1 mol / 75.07 g) = 0.378 mol
Calculation of moles is based on the molar mass of glycine.
How many moles of sucrose, C12H22O11, are in a 25-g sample of sucrose?
0.073 mol
This is calculated using the molar mass of sucrose.
Vitamin C is a covalent compound with the molecular formula C6H8O6. The recommended daily dietary allowance of vitamin C for children aged 4–8 years is 1.42 x 10^−4 mol. What is the mass of this allowance in grams?
0.0250 g
1.42 x 10^-4 mol (176.124 g / 1 mol) = 0.0250 g
What is the mass of 0.443 mol of hydrazine, N2H4?
14.2 g
The mass is calculated using the molar mass of hydrazine.
A packet of an artificial sweetener contains 40.0 mg of saccharin (C7H5NO3S). Given that saccharin has a molar mass of 183.18 g/mol, how many saccharin molecules are in a 40.0 mg (0.0400 g) sample of saccharin? How many carbon atoms are in the same sample?
1.31 x 10^20 C7H5NO3S molecules & 9.17 x 10^20 C atoms
0.0400 g (1 mol / 183.18 g) (6.022 x 10^23 / 1 mol) = 1.31 x 10^20
1.31 x 10^20 (7 C atoms / 1 C7H5NO3S molecule) = 9.17 x 10^20
How many C4H10 molecules are contained in 9.213 g of this compound?
9.545 × 10^22 molecules C4H10
How many hydrogen atoms are in 9.213 g of C4H10?
9.545 × 10^23 atoms H
