A. the mass in grams of one mole of a substance
<span>X: Geothermal energy
Y: Nonrenewable
So the answer is A</span>
Answer:
a)
⇒![Fe^{3+}+e^-](https://tex.z-dn.net/?f=Fe%5E%7B3%2B%7D%2Be%5E-)
⇒![2Br^-](https://tex.z-dn.net/?f=2Br%5E-)
b)
⇒![Mg^{2+}+2e^-](https://tex.z-dn.net/?f=Mg%5E%7B2%2B%7D%2B2e%5E-)
⇒![Cr^{3+}](https://tex.z-dn.net/?f=Cr%5E%7B3%2B%7D)
Explanation:
A)
Remember that positive number superscripts mean electrons lack and negative numbers mean electrons 'excess' (if we compare it with the neutral element). So, for the case of Fe2+ which is converted to Fe3+, we know that in Fe2+ there is a two electrons lack, while in Fe3+ there is a 3 electrons lack; it means that Fe2+ was converted to Fe3+ but releasing one electron:
⇒![Fe^{3+}+e^-](https://tex.z-dn.net/?f=Fe%5E%7B3%2B%7D%2Be%5E-)
The same analysis is applied to Br2; Br2 is a molecule which is said to have a zero superscript because it is an apolar covalent bond; and it is converted to Br-, which, according to what I wrote above, means that there is a one electron excess. So, Br2 must have received an electron in order to change to Br-; but Br2 can't change to Br- as simple as that because Br2 is a molecule, not an atom; it is a molecule that has two Br atoms, so, Br2 must give two Br- ions as products, but receiving one electron for each one:
⇒![2Br^-](https://tex.z-dn.net/?f=2Br%5E-)
b)
Applying the same, in Mg2+ there is a 2 electrons lack, and in Mg is not electron lack (its superscript is zero), so Mg must have released two electrons in order to change to Mg2+:
⇒![Mg^{2+}+2e^-](https://tex.z-dn.net/?f=Mg%5E%7B2%2B%7D%2B2e%5E-)
Cr3+ has a 3 electrons lack, and Cr2+ a two electrons one, so, Cr3+ must receive an electron to convert to Cr2+:
⇒![Cr^{3+}](https://tex.z-dn.net/?f=Cr%5E%7B3%2B%7D)
Hess's Law describes the conservation of energy in chemical reactions, stating that the heat flow of a reaction is equal to the sum of the heat flow of its composite reactions. A calorimeter measures the heat flow by creating a closed-system that contains the reaction. Ideally, a reading from the calorimeter would show the exact change in heat that a given reaction requires; however, the calorimeter absorbs an amount of heat from the system. Calculating the Qcal, the heat of the calorimeter, allows you to adjust your readings to determine the total heat flow of a reaction.
This website will help you to find it:
http://chemistry.tutorvista.com/physical-chemistry/specific-heat-capacity.html?view=simple
solution:
Calculate the molar concentration of the polycyclic aromatic hydrocarbon(PHA)(178.23g/mol),that was found in a well water sample at a concentration of 6.21ppb.Assume the density of the water is 1.00mg/mL![ppb corresponds to 1\mu g in 1L of sample \\the 6.21 ppb is 6.21\mu g in 1L of sample\\6.21\mu g PHA\times\frac{1mg PHA}{1000\mu g PHA}\times\frac{1g PHA}{1000\mu mg PHA}\times\frac{1mol. PHA}{178.23g PHA}\\3.48\times10^-8mol PHA\\and if we have 1L of solution\\m=\frac{moles}{v(L)}=\frac{3.48\times10^-8mol}{1L}\\3.348\times^10-8 M](https://tex.z-dn.net/?f=ppb%20corresponds%20to%201%5Cmu%20g%20in%201L%20of%20sample%20%5C%5C%3C%2Fp%3E%3Cp%3Ethe%206.21%20ppb%20is%206.21%5Cmu%20g%20in%201L%20of%20sample%5C%5C%3C%2Fp%3E%3Cp%3E6.21%5Cmu%20g%20PHA%5Ctimes%5Cfrac%7B1mg%20PHA%7D%7B1000%5Cmu%20g%20PHA%7D%5Ctimes%5Cfrac%7B1g%20PHA%7D%7B1000%5Cmu%20mg%20PHA%7D%5Ctimes%5Cfrac%7B1mol.%20PHA%7D%7B178.23g%20PHA%7D%5C%5C%3C%2Fp%3E%3Cp%3E3.48%5Ctimes10%5E-8mol%20PHA%5C%5C%3C%2Fp%3E%3Cp%3Eand%20if%20we%20have%201L%20of%20solution%5C%5C%3C%2Fp%3E%3Cp%3Em%3D%5Cfrac%7Bmoles%7D%7Bv%28L%29%7D%3D%5Cfrac%7B3.48%5Ctimes10%5E-8mol%7D%7B1L%7D%5C%5C%3C%2Fp%3E%3Cp%3E3.348%5Ctimes%5E10-8%20M)