Chemistry: An Introduction

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Questions and Answers

What distinguishes a substance from a mixture?

A substance has a uniform composition, while a mixture does not. (correct)

A substance can be physically separated into its components, while a mixture cannot.

A substance is always a single element, while a mixture can include multiple elements.

A substance contains only one kind of particle, while a mixture contains two or more. (correct)

Which of the following represents a homogeneous mixture?

Oil and vinegar

Sand and water

Salt dissolved in water (correct)

Fruit salad

What are the seven basic SI units?

Meter, liter, kilogram, energy, second, mole, and candela

Meter, kilogram, second, ampere, kelvin, mole, and candela (correct)

Liter, gram, second, volt, ohm, meter, and candela

Meter, pound, aston, second, kelvin, mole, and joule

In scientific notation, how is the number 0.0045 expressed?

4.5 × 10^-3 Signup and view all the answers

What does Dalton's Atomic Theory state about atoms of different elements?

They have distinct masses and properties. Signup and view all the answers

Which statement about significant figures is correct?

All non-zero digits are significant. Signup and view all the answers

What is molecular mass?

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

Which of the following prefixes represents a factor of 10^3?

kilo Signup and view all the answers

What is the molar volume of a gas at standard temperature and pressure (STP)?

22.4 L Signup and view all the answers

How would you calculate the number of moles from a given mass and molar mass?

moles = mass / molar mass Signup and view all the answers

What is the normality (N) of a solution if it contains 0.5 moles of an acidic solute that can donate 2 hydrogen ions?

2.0 N Signup and view all the answers

Which of the following correctly defines molality (m)?

moles of solute per kilogram of solvent Signup and view all the answers

Which of the following statements about mass and weight is true?

Weight is the force exerted due to gravity on an object. Signup and view all the answers

What is the correct formula to determine the mass of solute in a solution?

mass = moles × molar mass Signup and view all the answers

Which concentration term represents the ratio of the number of moles of one component to the total number of moles in a solution?

Mole Fraction Signup and view all the answers

What is the empirical formula?

The simplest whole-number ratio of atoms in a compound Signup and view all the answers

Study Notes

Chemistry: An Introduction

Chemistry is the branch of science studying the properties, preparation, structure, and composition of matter.
Matter is anything with mass that occupies space, while a substance is composed of only one kind of particle or has a fixed ratio of different particles.
Mixtures are combinations of substances. They can be classified into homogeneous mixtures (uniform throughout, like salt dissolved in water) and heterogeneous mixtures (non-uniform, like sand and water).
Constituent particles are the building blocks of matter. They are categorized as atoms, ions (charged particles like positively charged sodium ions), and molecules (combinations of atoms like water molecules).

Key Concepts in Chemistry

Units: Used to measure and quantify physical quantities. There are seven basic SI (Système International d'Unités) units:
- Length: Meter (m)
- Mass: Kilogram (kg)
- Time: Second (s)
- Electric Current: Ampere (A)
- Temperature: Kelvin (K)
- Amount of Substance: Mole (mol)
- Luminous Intensity: Candela (cd)
Prefixes: Used to represent multiples or fractions of units:
- deci (d): 10^-1
- centi (c): 10^-2
- milli (m): 10^-3
- micro (μ): 10^-6
- nano (n): 10^-9
- pico (p): 10^-12
- deca (da): 10¹
- hecto (h): 10²
Scientific Notation: Expressing numbers in the form x × 10ⁿ, where "x" is a non-zero number to the left of the decimal point and "n" is an integer.
Significant Figures: The digits in a measurement that are certain along with one uncertain digit.
- Non-zero digits are always significant.
- Zeros between non-zero digits are significant.
- Zeros to the right of a decimal place and after a non-zero digit are significant.
- Zeros to the left of a decimal place and before a nonzero digit are not significant.
- Zeros to the right of a decimal point and before a non-zero digit are significant.
Dalton's Atomic Theory: Formulated by John Dalton, it states:
- All atoms of a given element are identical in mass and properties.
- Atoms of different elements have different masses and properties.
- Matter is composed of indivisible particles called atoms.
- Chemical compounds are formed by the combination of atoms in fixed whole-number ratios.
- Atoms are neither created nor destroyed in chemical reactions.
Molecular Mass: The sum of the atomic masses of all atoms present in a molecule. It is expressed in unified atomic mass units (u).
Molar Concept: A mole is a unit of amount of substance equal to 6.022 × 10²³ particles (Avogadro's number - N_A).

Applying the Molar Concept

Calculating Moles:
- Given mass: moles = mass / molar mass
- Given number of particles: moles = number of particles / Avogadro's number
- Given volume at STP: moles = volume / molar volume (22.4 L)
Calculating Other Quantities:
- Mass: mass = moles × molar mass
- Number of Particles: number of particles = moles × Avogadro's number
- Volume at STP: volume = moles × molar volume (22.4 L)

Concentration Terms

Mass Percentage: The mass of solute divided by the mass of solution, multiplied by 100%.
Volume Percentage: The volume of solute divided by the volume of solution, multiplied by 100%.
Mole Fraction (X): The ratio of the number of moles of one component to the total number of moles of all components in a solution.
Molarity (M): Number of moles of solute dissolved in 1 liter of solution.
Normality (N): Number of gram equivalents of solute dissolved in 1 liter of solution.
- Equivalent mass for an acid is its molar mass divided by the number of replaceable hydrogen ions (H⁺).
- Equivalent mass for a base is its molar mass divided by the number of replaceable hydroxide ions (OH^-).
- Equivalent mass for an ion is its molar mass divided by its charge.
Molality (m): Number of moles of solute dissolved in 1 kilogram of solvent.

Important Considerations

Mass vs. Weight: Mass is a measure of the amount of matter in an object, while weight is the force exerted on an object due to gravity.
Exact Numbers: Exact numbers have an infinite number of significant figures. For example, "2 bananas" has an infinite number of significant figures.
Molar Volume: The volume occupied by one mole of a gas at standard temperature and pressure (STP) is 22.4 L.
Limiting Reactant: The reactant that is completely consumed in a chemical reaction. The amount of product formed is limited by the reactant that is consumed first.
Molecular Formula: The actual formula representing the number and type of atoms in a molecule.
Empirical Formula: The simplest whole-number ratio of atoms in a compound.

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Description

This quiz covers the fundamental concepts of chemistry, including the properties and composition of matter, and the distinction between substances and mixtures. Additionally, it introduces basic SI units used in measuring physical quantities. Test your understanding of these essential ideas in chemistry!