AP Chemistry: Coulomb's Law + Percent Composition

What does the force of attraction depend on?

According to Coulomb's Law, the FOA has to do with the distance and charge

Which of the following best helps explain why an atom of Rb gas more easily loses an electron in a chemical reaction than an atom of Li gas

In the RbRb atom the valence electron is farther from its nucleus than the valence electron of LiLi is from its nucleus. Because the RbRb electron is farther from its nucleus, there is a weaker attraction and it is easier to lose.

A student obtains a 10.0g sample of a white powder labeled as BaCl2. After completely dissolving the powder in 50.0mL of distilled water, the student adds excess Na2SO4(s), which causes a precipitate of BaSO4(s) to form, as represented by the equation above. The student filters the BaSO4(s), rinses it, and dries it until its mass is constant. What could best be answered based on the results of the experiment?

Is the BaCl2(s)BaCl2(s) used in the experiment pure? The calculated number of moles of BaBa in the precipitate can be compared with the expected number of moles of BaBa in 10.0g 10.0g of BaCl2BaCl2. The presence of fewer moles of in the precipitate would imply that the BaCl2BaCl2 was not pure.

Why does the atomic radii of the elements in the nitrogen group in the periodic table possess the trend of an increasing atomic radius ?

The attractive force between the valence electrons and the nuclei of the atoms decreases. Going down the group, the net attraction of the valence electrons for the nucleus decreases; thus the valence electrons maintain a greater average distance from the nucleus.

Which of the following best helps to explain why the atomic radius of K is greater than that of Br?

The effective nuclear charge experienced by valence electrons is smaller for KK than for Br. Because the effective nuclear charge of KK is smaller than that of BrBr, the attraction between its valence electron and the nucleus is less than the attraction between the valence electrons in BrBr and the nucleus.

A vessel contains a mixture of gases. The mass of each gas used to make the mixture is known. Which of the following information is needed to determine the mole fraction of each gas in the mixture?

The molar mass of each gas. The mole fraction of each gas is equal to the number of moles of the gas divided by the total number of moles of gases in the mixture. Given the mass of each gas, the molar mass of each gas is needed to determine the number of moles for each gas and the total number of moles in the mixture.

Which of the following best helps explain why the first ionization energy of K is less than that of Ca?

The valence electron of KK experiences a lower effective nuclear charge than the valence electrons of CaCa. The amount of energy required to remove the electron (IE1IE1) will depend on the strength of the attractive force between the electron and the nucleus, as predicted by Coulomb's law.

True or False: Smaller atoms have stronger bonds and atoms with greater charge have stronger bonds?

True; according to Coulomb's Law, smaller atom have a shorter distance from the nucleus to the electron. Atoms with larger charges have a more effective nuclear charge, and thus, a stronger bond

What is Coulomb's Law?

directly proportional to the charge, inversely proportional to the square of the distance; F=kq1q2/r^2

In regards to Coulomb's Law, which has more influence on the force of attraction?

the distance, however if the atoms are similar in distance, the larger charge has the advantage

What is the percent composition?

the percent by mass of each element in a compound