General Chemistry
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The plum-pudding model of the atom predicted the structure of an atom. In this model, the electrons are embedded ('plums') in a positively charged 'pudding'. If this is the accurate model of the atom, what would be the outcome of Rutherford's experiment?
Which of the following is a conclusion made about the structure of an atom based on Rutherford's gold foil experiment?
Identify the statements that are correct based only on Rutherford's nuclear theory as it was originally stated
i. Neutral helium atoms contain more electrons than protons.
ii. The atom's volume is mostly empty space.
iii. The nucleus of an atom composes most of the volume of an atom.
iv. Neutral helium atoms contain more protons than neutrons.
The approximate diameter of a gold atom is 270 pm and its nucleus has a diameter of 1.0 x 10–2 pm. Calculate the fraction of the α particles in Rutherford's gold foil experiment that are scattered at large angles by using the cross-sectional area occupied by the nucleus as a fraction of that occupied by the atom. Assume a gold foil that is 4 layers thick with the nuclei equally offset from each other such that no crosssection overlaps.
Determine which statement(s) is/are inconsistent with Rutherford's atomic theory.a. An oxygen atom has 8 protons in its nucleus so there should be 8 electrons outside its nucleus.b. Most of the mass of a chlorine atom is due to its 17 electrons.c. Since protons are larger than electrons and a hydrogen atom only contains one proton and one electron, the volume of a hydrogen atom is mostly because of its proton.d. A sulfur atom has 16 protons in its nucleus and 25 electrons outside of its nucleus.
In the experiment done by Ernest Rutherford concerning alpha particle scattering by gold foil concluded that:
Which significant conclusion was drawn from Rutherford's gold foil experiment?
What are the main subatomic particles that contribute to the majority of the mass of the atom?
There are two different isotopes of chlorine and these are 35Cl (abundance = 75.78 %) and 37Cl (abundance = 24.22 %). Under a certain condition, a mass spectrum of Cl2 consists of three peaks (Peak 1 - 69.938 u, Peak 2 - 71.935 u, and Peak 3 - 73.932 u) with a relative abundance ratio of 9:6:1. Determine which two atoms comprising a Cl2 molecule gave each peak.
Assuming no decomposition into constituent isotopes and that the mass spectrum of Br2 showed only three peaks, determine the relative masses of the peaks in four significant figures. Note that the two naturally occurring isotopes of bromine are 79Br (mass = 78.91834 u; abundance = 50.69 %) and 81Br (mass = 80.91629 u; abundance = 49.31 %).
When the molecular weight of acetone is calculated using the atomic weights found in the periodic table the value would be 58.07891. However, the molecular weight obtained from high-resolution mass spectrometry will give a slightly different value. Which of the following statements explains this difference in weight?
In a mass spectrometer, why are gaseous samples bombarded with a beam of high-energy electrons?
The element silver has two naturally occurring isotopes. The isotope 107Ag has a mass of 106.905 and the isotope 109Ag has a mass of 108.905. Which of the following is the mass spectrum of a sample of silver atoms given that the atomic weight of silver is 107.868?
Sulfur has four naturally occurring stable isotopes, three of which (32S, 33S, 34S) are more abundant than the fourth (36S). The mass spectrum of hydrogen sulfide (H2S) consists of three molecular ion peaks:
Calculate the average molecular weight for the H2S molecule.
Identify the following statement as correct or incorrect. If it is false, change the statement so that it becomes correct.The intensity of a peak in a mass spectrum is directly proportional to the relative abundance of that isotope.
Sulfur has four naturally occurring stable isotopes, three of which (32S, 33S, 34S) are more abundant than the fourth (36S). The mass spectrum of hydrogen sulfide (H2S) contains three molecular ion peaks:
What is the origin of the third peak? (Which sulfur isotope does it arise from?)
Phosphorous-32 is a radioactive isotope of phosphorous and undergoes a beta decay to yield sulfur-32. If the two isotopes are to be differentiated using a mass spectrometer, what should be the precision of the mass spectrometer that is able to differentiate between the two?
When a sample of iodine is analyzed using mass spectrometry, the mass spectrum shows a large peak at 126.904. However, the mass spectrum of bromine does not show a peak at 79.904 (the atomic mass of bromine). Why is it so?
In mass spectrometry, the mass of a cation is taken as the mass of the atom from which the cation was formed even though the cation is missing electrons. Calculate what percent of the mass of a lithium-7 atom is represented by two electrons. Is this percentage significant?
Nitrogen has two stable isotopes: Nitrogen-14 and nitrogen-15. If a sample of nitrogen gas (N2) is analyzed using mass spectrometry, the following peaks (relative height in parenthesis) are obtained: m/z 28 (100 %); m/z 29 (0.731 %); m/z 30 (0.001 %). Using this data, calculate the abundance of each isotope.
Mass spectrometry can reveal the presence of isotopes of an element in a compound being analyzed. Isotopes, as separate peaks, can most easily be seen next to the molecular ion peak. Chlorine has two isotopes: Chlorine-35 (abundance 76 %) and chlorine-37 (abundance 24 %). If chloromethane (CH3Cl) is subjected to mass spectrometry, how many molecular ion peaks will the mass spectrum have?
Mass spectrometry can reveal the presence of isotopes of an element in a compound being analyzed. Isotopes, as separate peaks, can most easily be seen next to the molecular ion peak. Bromine has two isotopes: Bromine-79 (abundance 51 %) and bromine-81 (abundance 49 %). If bromomethane (CH3Br) is subjected to mass spectrometry, how will the bromine isotopes appear on the mass spectrum?
Determine if the following statement about a mass spectrometer is true or false: Heavier ions are deflected to a greater extent than lighter ions.
Determine the atomic mass of thallium from the mass spectrum of thallium shown below:
Find the atomic mass of germanium based on the mass spectrum below. Use the graph and determine the approximate mass and percent intensity values. Use two significant figures.
The mass spectrum for the stable isotopes of iron (54Fe, 56Fe, 57Fe, and 58Fe) is shown below.
Calculate the average atomic mass of iron using the data above and compare it with the periodic table value.
Which among the following subatomic particles (electron, proton, or neutron) was the most difficult to discover? Why?