2HCO3 - + Ca2+ CaCO3 + CO2 + H2O Bicarbonate (HCO3-) combines with calcium ions in the water to make calcium carbonate (CaCO3, limestone). This process can occur both within organisms such as corals or as a simple chemical reaction in the water itself.
![176.0 \; \text{kJ} \cdot \text{mol}^{-1}](https://tex.z-dn.net/?f=176.0%20%5C%3B%20%5Ctext%7BkJ%7D%20%5Ccdot%20%5Ctext%7Bmol%7D%5E%7B-1%7D)
As long as the equation in question can be expressed as the sum of the three equations with known enthalpy change, its
can be determined with the Hess's Law. The key is to find the appropriate coefficient for each of the given equations.
Let the three equations with
given be denoted as (1), (2), (3), and the last equation (4). Let
,
, and
be letters such that
. This relationship shall hold for all chemicals involved.
There are three unknowns; it would thus take at least three equations to find their values. Species present on both sides of the equation would cancel out. Thus, let coefficients on the reactant side be positive and those on the product side be negative, such that duplicates would cancel out arithmetically. For instance,
shall resemble the number of
left on the product side when the second equation is directly added to the third. Similarly
Thus
and
![-\frac{1}{2} \times (1) + \frac{1}{2} \times (2) - \frac{1}{2} \times (3)= (4)](https://tex.z-dn.net/?f=-%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20%281%29%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20%282%29%20-%20%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20%283%29%3D%20%284%29)
Verify this conclusion against a fourth species involved-
for instance. Nitrogen isn't present in the net equation. The sum of its coefficient shall, therefore, be zero.
![a + b = -1/2 + 1/2 = 0](https://tex.z-dn.net/?f=a%20%2B%20b%20%3D%20-1%2F2%20%2B%201%2F2%20%3D%200)
Apply the Hess's Law based on the coefficients to find the enthalpy change of the last equation.
![\Delta H _{(4)} = -\frac{1}{2} \; \Delta H _{(1)} + \frac{1}{2} \; \Delta H _{(2)} - \frac{1}{2} \; \Delta H _{(3)}\\\phantom{\Delta H _{(4)}} = -\frac{1}{2} \times (-628.9)+ \frac{1}{2} \times (-92.2) - \frac{1}{2} \times (184.7) \\\phantom{\Delta H _{(4)}} = 176.0 \; \text{kJ} \cdot \text{mol}^{-1}](https://tex.z-dn.net/?f=%5CDelta%20H%20_%7B%284%29%7D%20%3D%20-%5Cfrac%7B1%7D%7B2%7D%20%5C%3B%20%5CDelta%20H%20_%7B%281%29%7D%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5C%3B%20%5CDelta%20H%20_%7B%282%29%7D%20-%20%5Cfrac%7B1%7D%7B2%7D%20%5C%3B%20%5CDelta%20H%20_%7B%283%29%7D%5C%5C%5Cphantom%7B%5CDelta%20H%20_%7B%284%29%7D%7D%20%3D%20-%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20%28-628.9%29%2B%20%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20%28-92.2%29%20-%20%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20%28184.7%29%20%5C%5C%5Cphantom%7B%5CDelta%20H%20_%7B%284%29%7D%7D%20%3D%20176.0%20%5C%3B%20%5Ctext%7BkJ%7D%20%5Ccdot%20%5Ctext%7Bmol%7D%5E%7B-1%7D)
Answer:
X 86 206
Explanation:
Radioactive atoms are nuclei that can under go disintegration to emit either an alpha particle, beta particle or gamma radiation. The process could be spontaneous or stimulated.
When a radioactive atom R 88 210 emits alpha particle, it would produce an element with atomic number 86 and mass number 206 i.e X 86 206. An alpha particle is usually a helium nucleus.
⇒
+
+ energy
Let's write the equation
![\\ \sf\longmapsto {NaOH\atop ?}+{HCl\atop 73g}\longrightarrow {NaCl\atop 117g}+{H_2O\atop 36g}](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Clongmapsto%20%7BNaOH%5Catop%20%3F%7D%2B%7BHCl%5Catop%2073g%7D%5Clongrightarrow%20%7BNaCl%5Catop%20117g%7D%2B%7BH_2O%5Catop%2036g%7D)
According to law of conservation of mass .
- Mass of products=Mass of reactants
Let required value be x
![\\ \sf\longmapsto x+73=117+36](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Clongmapsto%20x%2B73%3D117%2B36)
![\\ \sf\longmapsto x+73=153](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Clongmapsto%20x%2B73%3D153)
![\\ \sf\longmapsto x=153-73](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Clongmapsto%20x%3D153-73)
![\\ \sf\longmapsto x=80g](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Clongmapsto%20x%3D80g)
Mesosaurus lived in freshwater lakes and ponds. Elongated and slim, it measured about 3.3 feet long. The skull and tail were both long and narrow, and the animal probably undulated through the water as it fed on small crustaceans and other prey with its jaws, which were full of long, thin, pointed teeth.