Exam 1: A Very Brief History of Chemistry

A naturally occurring element consists of two isotopes. The data for the isotopes are: Isotope 1 68.5257 u 60.226 % Isotope 2 70.9429 u ------ % Calculate the average atomic mass of this element. Hint: Percentages should always add up to 100% then find the weighted average.

A compound of phosphorus and chlorine contains 3.00 grams of phosphorus and 10.3 grams of chlorine. There are ________ total grams of the compound in a sample that contains 4.00 grams of chlorine. Hint: Consider the ratio of the masses to determine the mass of compound.

Which description below fits the ¹¹²Cd atom?

The element bromine has two main isotopes that result in almost all bromine on Earth. The two are listed below with their atomic masses. The average atomic mass of bromine is listed as 79.904 u. Using this information what is the relative abundances of the two chlorine isotopes? Bromine-79: 78.918 u Bromine-81: 80.916 u ,Hint: Set up a weighted average calculation where one percentage is x and the other percentage is (100 - x).

Microwave radiation observed by Penzias and Wilson in 1964 helps to support the big-bang theory because it observed microwave radiation that was characteristic of a temperature that matched the predicted temperature of the universe after heating up for 14 billion years.

One would expect a fairly even distribution of elements on the earth; instead, the distribution is uneven. Which of the following best describes why we observe this?

The element chlorine has two main isotopes that result in almost all chlorine on Earth. The two are listed below with their atomic masses. The average atomic mass of chlorine is listed as 35.453 u. Using this information what is the relative abundances of the two chlorine isotopes? Chlorine-35: 34.969 u Chlorine-37: 36.966 u ,Hint: Set up a weighted average calculation where one percentage is x and the other percentage is (100 - x).

In a chemical compound, the elements are always combined in the same proportions by ________.

According to the Law ________, there is no gain or loss of mass in chemical reactions.

A naturally occurring element consists of three isotopes. The data for the isotopes are: Isotope 1: 187.9122 u., 10.861% Isotope 2: 190.9047 u, ------% Isotope 3: 192.8938 u, 76.711% What is the average atomic mass of this naturally occurring element? Hint: Percentages should always add up to 100% then find the weighted average.

The atomic mass of naturally occurring silver, which is a mixture of two isotopes, is listed as 107.868 u. This means that ,Hint: Individual atoms have a mass number that is the sum of the protons and neutrons.

Based on the law of Conservation of Mass, 1.2 g of elemental carbon (C)reacts with molecular oxygen (O₂)to produce 4.4 g of carbon dioxide gas (CO₂)as the only product. What mass of oxygen reacts?

The atomic mass of naturally occurring cobalt, which exists in nature as a single isotope, is listed as 58.9332 u. This means that

The species shown below that has 24 neutrons is

The major isotopes of tungsten (with abundances shown)are ¹⁸²W (26.32%), ¹⁸³W (14.31%), ¹⁸⁴W (30.67%), and ¹⁸⁶W (28.62%). What is the atomic mass of tungsten?

Atoms are made of tiny particles called molecules.

Which of the following is consistent with the postulates from Dalton's atomic theory?

A neutral iodine atom has an atomic mass number = 131. Which description below fits this atom?

Assuming that most of the mass of the universe is found in stars, why is hydrogen still the most common element in the universe? Hint: Consider the kinetic energy of the particles and how kinetic energy can affect them coming together.

Which answer below best describes all atoms of a given isotope of a particular element?