1. Ethanoic acid (acetic acid) is very soluble in water. However, naturally ocurring long-chain carboxylic acids such as palmitic acid (CH3(CH2)14COOH) are insoluble in water. Explain why.
My guess: Long-chain carboxylic acids have stronger relative strength of intermolecular forces between them, which made them unsoluble in water as they had strong intermolecular forces between their long carbon chains.
2. Why did the characteristics below apply to transition metals?
a. Ions vary in charge.
b. Many of their solids are colored.
c. Many are hard solids.
My guess:
a. It was because unpaired Delectrons can move to the outer energy level, such that they can form ions vary in charge.
b. No ideas.
c. They had more unpaired electrons in the d sublevel? This made their melting and boiling pionts higher and thus increase their hardness?
Thank you!
1. Like dissolves like. The COOH group on the palmitic acid is an acid, it is polarized (and polarizable) and it is the water loving part. Small organic molecules containing these groups are soluble since the organic non-polar part is a small part of the molecule. As the chain length increases, however, the non-polar part increases to the point that the organic part outweighs the water soluble part and the entire molecule is not soluble. (I think you would do better to use insoluble than unsoluble.). Another point is that the COOH portion can form hydrogen bonds, both with other COOH molecules as well as water while the organic portion has only dispersion forces between molecules.
2a. Your answer is ok but it's more like this. The ionization potential difference is relatively small between s,p, and d electrons, so the atoms show variable oxidation states because of this.
2b. The fact that we see color is due almost entirely to unpaired electrons.
2c. It has been suggested that the d electrons are being used to build the crystal lattice; thus making the solid crystals harder.
1. Your guess is partially correct. The solubility of carboxylic acids in water is determined by their ability to form hydrogen bonds with water molecules. Ethanoic acid (acetic acid) is highly soluble in water because it can form hydrogen bonds with the water molecules due to the presence of the polar carboxyl (-COOH) group. However, long-chain carboxylic acids like palmitic acid have a nonpolar hydrocarbon chain, which is insoluble in water because it cannot form strong hydrogen bonds with water. The intermolecular forces between the long carbon chains in long-chain carboxylic acids are indeed stronger than the interactions between the acids and water, but the primary reason for insolubility lies in the inability to form hydrogen bonds with water.
2. Let's go through each characteristic and explain why it applies to transition metals:
a. Ions vary in charge: Transition metals have the ability to exhibit variable oxidation states or charges. This is because their d-electron configuration allows for the movement of electrons between different energy levels. This flexibility in electron movement enables the formation of ions with different charges.
b. Many of their solids are colored: The color of transition metal compounds arises due to the presence of partially filled d-orbitals. When light interacts with these compounds, some wavelengths are absorbed, while others are transmitted or reflected. The absorbed wavelengths correspond to certain colors, giving rise to the observed color in transition metal compounds.
c. Many are hard solids: Transition metals tend to have high melting and boiling points, leading to the formation of hard solids. This is attributed to the presence of strong metallic bonding, which arises from the delocalization of d-electrons. More unpaired d-electrons in the d-sublevel can contribute to stronger metallic bonding and higher melting and boiling points, thus leading to harder solids.
Overall, the unique electron configuration and bonding properties of transition metals contribute to their varying charge ions, colored compounds, and hard solid characteristics.