General Chemistry Exam 1
The speed of sound in air is 344 m/s at room temperature. The lowest frequency of a large organ pipe is 30 s^-1 and the highest frequency of a piccolo is 1.5 x 10^4 s^-1. Find the difference in wavelength.
Organ - 344 m/s / 30 = 11.4666 m Piccolo - 344 m/s / 1.5 x 10^4 = 0.0229 m
How many protons and neutrons are present in an atom of 39,19K?
Protons = 19, Neutrons = 20 (the bottom number is protons. Subtract bottom number from top number to solve for neutrons)
According to Rutherford's experiment, what contributes the most to the atom's mass?
The atom core
Explain the difference between Z(atomic number) and A(mass number)
The atomic number, Z, is the number of protons in an atom's nucleus. The atomic Mass number, A, is the sum of the neutrons and protons in an element.
As the wavelength of electromagnetic radiation increases ___________
The frequency decreases and the energy per photon decreases.
Atomic Number
Z - number of protons
What is a photon?
a particle of light
What is a pure substance?
a substance in which there is only one type of particle and its composition cannot vary from one sample to another
What theory did John Dalton formulate?
atomic theory- a theory that each element is composed of tiny indestructible particles called atoms, that all atoms of a given element have the same mass and other properties, and that atoms combine in simple whole number ratios to form compounds.
What law did Lavoisier create?
law of conservation of mass
What defines an element?
number of protons in the nucleus
Define homogeneous mixture
same composition throughout, like alcohol & water mixed together
Rutherford's experiment conclusions
(a) The majority of space inside the atom is empty. (b) The atom contains a positively charged nucleus. (c) Positive charge is condensed in one location within the atom. (d) The mass of the atom is concentrated at the nucleus.
What are the main ideas in Dalton's atomic theory?
1. Atoms combine in simple, whole number ratios to form compounds. 2. Atoms of one element cannot change into atoms of another element. 3. Each element is composed of tiny, indestructible particles called atoms. 4. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
What is the symbol for the carbon isotope with 7 neutrons?
13,6 C (13 is written above the 6)
How many neutrons are found in 1 atom of 16N?
9 The atomic number for N is 7. The atomic number is equal to the number of protons in an element. To find neutrons, subtract atomic number from the mass number (16)
Atomic Mass Number
A - number of protons + number of neutrons
Define heterogeneous mixture
A mixture that has visibly different parts
Mass number (A)
A=Z+N, where N = number of protons in the nucleus
Gallium has two naturally occurring isotopes: Ga-69 with a mass of 68.9256 amu and a natural abundance of 60.11% and Ga-71. Use the atomic Mass of gallium from the P. T. to find the mass of Ga-71.
Atomic Mass of gallium = 69.72 68.9256(0.6011) + x(0.3989) = 69.72 41.4312 + 0.3989x = 69.72 0.3989x = 69.72 - 41.4312 0.3989x = 28.2918 X = 28.2918/0.3989 X = 79.9245 amu
What are the atomic number and mass number for the carbon isotope with 7 neutrons?
Atomic Number (Z) = 6, Mass Number (A) = 13. The atomic number for carbon is 6. The mass number is the atomic number + the number of neutrons.
Calculate atomic weight
Atomic weight = (mass * fractional abundance)a + (mass * fractional abundance)b
Identify the atom whose nucleus is composed of 56 protons and 82 neutrons.
Barium-138 (the number of protons identifies the atom)
How to calculate the number of molecules
Calculate number of moles (x / molar mass) then multiply by Avogadro's number
Calculate mass, in grams, of a single Iodine atom
Divide # of atoms by Avogadro's number then multiply by amu of Iodine (126.9)
How is the energy of a photon related to its frequency?
E = h x v (h, Planck's constant. v, frequency)
How is the energy of a photon related to its wavelength?
E=h x c / wavelength
What is the energy of a photon with a wavelength of 3.10 X 10^-17 m?
E=h[plancks constant] x c[speed of light] /wavelength (weird triangle shape) E = (6.626 x 10^-34) x (3x10^8) / (3.1 x 10^-17) E = 6.41 x 10^-19 J
Arrange the following types of electromagnetic radiation in order of increasing wavelength (shortest to longest) : microwaves, gamma rays, ultraviolet and infrared.
Gamma rays, ultraviolet, infrared and microwaves
What observations did Antoine Lavoisier make?
He noticed that there was no change in the total mass of material within the container during combustion.
