Chem 120 Final Exam 2 GRADED A ACTUAL EXAM

Chem 120 Final Exam 2 GRADED A+ (ACTUAL EXAM )

Questions and Answers (Solved)

• Dalton's Theory

Answer: All matter is composed of small invisible particles called atoms All atoms of a given element are alike in mass and other properties The atoms of one element are different from atoms of all other elements

• Law of Conservation of Mass

Answer: Matter is neither created nor destroyed

Atoms of one element cannot be changed into atoms of another element by chemical reactions

• law of definite proportions

Answer: a compound is always composed of the same elements in the same

proportion by mass Compounds are formed when atoms of more than one element combine

• Law of Multiple Proportions

Answer: When two atoms combine to form different com- pounds, their relative

masses can be described as a ratio of small, whole numbers

• Charged particles generate...

Answer: Electric fields and exert force on other particles

• Moving charges generate...

Answer: Magnetic fields which can deflect other moving charged particles

• Rutherford's experiment

Answer:

Experiment: shoot large, positively charged particles at a gold film

Results: proposed nuclear theory

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• nuclear theory

Answer: Nucleus- small core of atoms that contains 99.9% of mass Negatively

charged electrons dispersed #protons=#electrons

• mass number (A)

Answer: the total number of protons and neutrons in the nucleus of an atom

A= protons + neutrons

• What defines the elements symbol and identity?

Answer: # of protons

• atomic mass unit (amu)

Answer: a unit of mass equal to 1/12 the mass of a carbon-12 atom

The mass of an atom in AMU is protons+neutrons 1g= 6.022*10^-23amu

• Isotopes are

Answer: atoms of the same element with different atomic masses Isotopes have

different number if neutrons

• mass spectrometry

Answer: a technique that separates particles according to their mass

• Atomic mass

Answer: The weighted average of the masses of the isotopes of an element

Atomic mass= (fraction of isotope n)*(mass of isotope n)

• Ions are

Answer: Charged particles Different number of electrons

• Cations

Answer: Positively charged ions Lose e- 2 / 3

• Anion

Answer: A negatively charged ion Gain e-

• The International System of Units

Answer: SI

• SI base units

Answer: SI units from which all others can be derived

• significant figures

Answer: All the digits that can be known precisely in a measurement, plus a last estimated digit

• Precision

Answer: a measure of how close a series of measurements are to one another

• Accuracy

Answer: A description of how close a measurement is to the true value of the

quantity measured.

• Density

Answer: Mass / Volume

• intensive property

Answer: a property that depends on the type of matter in a sample, not the amount of matter

• extensive property

Answer: a property that depends on the amount of matter in a sample

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