Chem 2045 Exam 1 (Ch.1-3) Flashcards

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Questions and Answers

What is the molar mass of Ba3(PO4)2 if Ba = 137.3, P = 30.97, O = 16?

601.84

How many moles of Ba3(PO4)2 are in 60.0 grams of Ba3(PO4)2?

0.0997 mol

How many moles of O are present in the same sample as question 2?

0.7976 mol

How many oxygen atoms are in question 3?

4.803x10^23 Signup and view all the answers

What is the mass composition of O in Ba3(PO4)2?

21.27% Signup and view all the answers

How do you calculate empirical formula for a compound based on elemental mass compositions?

Convert mass to moles, write pseudoformula, divide by smallest subscript and clear fractions. Signup and view all the answers

What is the empirical formula for a compound based on the following elemental mass compositions: C 49.48%, H 5.19%, N 28.85%, O 16.48%?

C4H5N2O Signup and view all the answers

How do you calculate molecular formula?

Find empirical formula, find n (n = molar mass / empirical formula molar mass), multiply n by empirical formula subscripts. Signup and view all the answers

If the molar mass in slide 7 is 194.19 grams, what is the molecular formula?

C8H10N4O2 Signup and view all the answers

What does Rutherford's Theory state?

Protons are positive charge, neutrons are neutral, electrons are negative charge. Signup and view all the answers

What is atomic number (Z)?

Number of protons Signup and view all the answers

What is mass number (A)?

Number of protons + number of neutrons Signup and view all the answers

What is the formula for the number of protons?

A - Z Signup and view all the answers

What is an isotope?

Atoms with the same number of protons but different number of neutrons Signup and view all the answers

What is the atomic mass formula for isotopes?

(fraction of iso. 1 x mass of iso 1) + (fract. of iso. 2 x mass of iso. 2) + ... Signup and view all the answers

What is an example of an atomic mass problem involving boron?

10.8 amu Signup and view all the answers

What is an element?

Substance composed of a single type of atom Signup and view all the answers

What is a compound?

Substance composed of two or more elements in a fixed, definite proportion Signup and view all the answers

How are compounds held together?

Chemical bonds, which result from attractions between charged particles. Signup and view all the answers

What is a chemical formula?

It indicates the elements present in the compound and the relative number of atoms or ions of each. Signup and view all the answers

What is the name for an element that exists as a molecule?

Diatomic molecule Signup and view all the answers

What are the names of elemental groups?

Inner Transition metals: Lanthanides, Actinides; Main Table: Alkali metals, Alkaline earth metals, Halogens, Noble Gases. Signup and view all the answers

What are the types of ions?

Cations and Anions Signup and view all the answers

How do electrons in an atom make chemical bonds?

Like charges repel and opposite charges attract. Signup and view all the answers

What are the two types of chemical bonds?

Ionic and covalent Signup and view all the answers

What is an ionic bond?

The transfer of electrons from a metal to a nonmetal. Signup and view all the answers

What is a covalent bond?

The sharing of electrons between two nonmetals. Signup and view all the answers

What are atomic elements vs molecular elements?

Atomic elements exist as single atoms, while molecular elements exist as bonded pairs or groups of atoms. Signup and view all the answers

What are the bonds of molecular compounds?

Usually composed of two or more covalently bonded nonmetals. Signup and view all the answers

What are the bonds of ionic compounds?

Composed of cations and anions bound together by ionic bonds. Signup and view all the answers

What is an example of a polyatomic ion?

ClO− and HCO3− Signup and view all the answers

What are the properties of ionic compounds?

Typically solids with high melting points, non-conductive in solid form, conductive in molten form. Signup and view all the answers

What are the steps to write an ionic compound formula?

Positive and negative charges must balance, and the formula reflects the smallest whole-number ratio. Signup and view all the answers

What are basic polyatomic ions to memorize?

NH4+, CO32−, CH3COO−, HCO3−, OH−, PO43−, NO3−, ClO3−, NO2−, ClO4−, MnO4−, SO42−, Cr2O72−, SO32−. Signup and view all the answers

What are the types of ionic compounds?

Binary ionic compounds and polyatomic ionic compounds. Signup and view all the answers

How do you name binary compounds?

The first element is named as is, and the second element gets the -ide suffix. Signup and view all the answers

What are basic monoatomic ions to memorize?

Fluorine F−, Chlorine Cl−, Bromine Br−, Iodine I−, Oxygen O2−, Sulfur S2−, Nitrogen N3−, Phosphorus P3−. Signup and view all the answers

How do you name ionic compounds with polyatomic ions?

Use the name of the polyatomic ion whenever it occurs in the formula. Signup and view all the answers

What is a molecular compound?

Compounds composed of two or more covalently bonded nonmetals. Signup and view all the answers

How do you name molecular compounds?

Use prefixes for both nonmetals and change the second nonmetal's suffix to -ide. Signup and view all the answers

What is formula mass?

The sum of the atomic masses of all the atoms in the chemical formula of a molecule. Signup and view all the answers

How do you calculate formula mass?

By summing the products of the number of atoms of each element and their respective atomic masses. Signup and view all the answers

What is a mole?

The amount of material containing $6.022 × 10^{23}$ particles. Signup and view all the answers

How do you convert between number of particles and mass?

Using molar mass in combination with Avogadro's number. Signup and view all the answers

What do subscripts in a formula indicate?

The number of atoms of each type of element in a compound. Signup and view all the answers

What is an example of moles in a chemical formula?

1 mole of PBr3 contains 1 mole P and 3 moles Br. Signup and view all the answers

What is mass percent composition?

The percentage by mass of each element in the compound. Signup and view all the answers

What is an example of mass percent composition?

25% H and 75% C in a 10.0 g sample. Signup and view all the answers

What is the formula for mass percent composition?

(mass of an element / total mass of the compound) x 100% Signup and view all the answers

How can percent composition of a compound be calculated?

(mass of A in 1 mol of compound / molar mass of compound) x 100% Signup and view all the answers

What is a solution?

A homogeneous mixture of two or more substances. Signup and view all the answers

What is a solvent?

The solution component that is higher relative to other components. Signup and view all the answers

What is a solute?

The solution component present in a concentration less than that of the solvent. Signup and view all the answers

What is an aqueous solution?

A solution for which water is the solvent. Signup and view all the answers

What is molarity?

Unit of concentration, defined as moles of solute per liter of solution. Signup and view all the answers

What is the molarity (M) formula?

(amount of solute in mols / volume of solution in L) Signup and view all the answers

What is dilution?

The process whereby the concentration of a solution is reduced by adding solvent. Signup and view all the answers

What is the molarity formula for dilution?

M1V1 = M2V2 Signup and view all the answers

Study Notes

Molar Mass and Mole Calculations

Molar mass of Ba3(PO4)2 is 601.84 g/mol, calculated using individual atomic masses.
60.0 grams of Ba3(PO4)2 equates to 0.0997 moles using the formula: grams x (1 mol/molar mass).
Amount of oxygen in 0.0997 moles of Ba3(PO4)2 is 0.7976 moles, calculated using the ratio of oxygen in the compound.

Avogadro's Number and Atoms

Number of oxygen atoms in 0.7976 moles is 4.803 x 10^23, determined using Avogadro's number.
Avogadro's number (6.022 x 10^23) indicates the quantity in one mole of any element.

Mass Composition and Empirical Formulas

Mass composition of oxygen in Ba3(PO4)2 is 21.27%, found by dividing mass of oxygen by total molar mass and multiplying by 100%.
To find an empirical formula from mass compositions: convert mass to moles, write a pseudoformula, and simplify by dividing by the smallest subscript.

Molecular Formulas

The molecular formula is derived from the empirical formula and molar mass using the relationship n = molar mass/empirical formula mass.
Given a molar mass of 194.19 grams and an empirical formula mass of 97.1, the molecular formula is C8H10N4O2.

Atomic Structure

Rutherford's theory describes protons (positive), neutrons (neutral in nucleus), and electrons (negative, in empty space).
Atomic number (Z) indicates the number of protons, defining the element; mass number (A) is the total of protons and neutrons.

Isotopes and Atomic Mass

Isotopes have the same number of protons but different neutrons, resulting in different masses but similar chemical behaviors.
Atomic mass is calculated as a weighted average of isotopic masses based on their natural abundance.

Chemical Bonds and Compounds

Compounds consist of two or more elements bonded chemically through ionic or covalent bonds.
Ionic bonds involve electron transfer between metals (cations) and nonmetals (anions), while covalent bonds involve electron sharing between nonmetals.

Types of Elements

Atomic elements consist of single atoms (e.g., He, Na), while molecular elements consist of bonded atoms (e.g., diatomic H2, O2).

Ionic and Molecular Compounds

Ionic compounds consist of cations and anions creating a formula unit, while molecular compounds consist of covalently bonded nonmetals forming molecules.
Naming conventions differ: binary ionic compounds are named with -ide endings for anions; polyatomic ions maintain their names.

Percent Composition and Solutions

Mass percent composition is the percentage by mass of each element in a compound, calculated as (mass of element/total mass) x 100%.
Solutions consist of a solute (lesser amount) dissolved in a solvent (greater amount), often water in aqueous solutions.

Molarity and Dilutions

Molarity (M) is a concentration unit defined as moles of solute per liter of solution, calculated using M = (amount of solute in mols/volume of solution in L).
The dilution equation M1V1 = M2V2 allows for the calculation of molarity in diluted solutions.

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Test your knowledge with these flashcards for Chem 2045 Exam 1, covering key concepts from Chapters 1 to 3. Topics include molar mass calculations and moles in chemical compounds. Perfect for reviewing essential chemistry concepts before your exam.