Answer:
The change in enthalpy is +210 kJ, so it is an endothermic reaction.
Explanation:
- The change in enthalpy shows that the reaction is exothermic or endothermic.
The change in enthalpy = The energy of products - the energy of reactants.
- If ΔH is positive value, the reaction is endothermic, the energy of the products is higher than that of the reactants.
- If ΔH is negative value, the reaction is exothermic, the energy of the products is lower than that of the reactants.
<em>For this reaction: </em>The change in enthalpy = The energy of products - the energy of reactants = 370 kJ - 160 kJ = + 210 kJ.
<em>So, the right choice is: The change in enthalpy is +210 kJ, so it is an endothermic reaction.</em>
Answer:
The cis double bond present in unsaturated fatty acids acids results in lower melting point when compared to saturated fatty acids of the same chain length.
Explanation:
Melting point of a fatty acids are affected by the length and degree of unsaturation of the hydrocarbon chain.
At room temperature, saturated fatty acids with hydrocarbon chain lengths between 12-24 are waxy solids whereas unsaturated atty acids of the same chain length are liquids. This is due to the nature of the packing of the fatty acid molecules in the saturated and unsaturated compounds.
In the saturated compounds, the molecules are tightly packed side by side with minimal steric hindrance and maximal van der Waals forces of attraction between molecules. However, in unsaturated fatty acids, the cis double bond introduces a bend or kink in the molecules which then interferes with the tight packing of the molecules and reducing interaction between molecules. Therefore, less energy is required to cause a disorder in the arrangement of unsaturated fatty acids, leading to a lowering of melting point.
In the question, the number of atoms per unit cell is required for:
A) Polonium (Po)
In polonium, the structure is simple cubic, meaning there are 8 corner atoms, which add up to one atom per unit cell.
B) Manganese (Mn)
The structure of the Mn can be considered to be a body centered cubic (BCC) and the number of atoms for this is 8 corner atoms and 1 central atoms, making a total of 2 atoms per unit cell.
C) Silver (Ag)
Silver has a face centered cubic (FCC) unit cell structure, where there are 8 corner atoms and 6 atoms on the faces, so there are a total of 4 atoms per unit cell.
