It's called a nebula or nebulae (plural). They are not only massive clouds of dust, hydrogen and helium gas, and plasma; they are also often “stellar nurseries” – i.e. the place where stars are born.
There are 3 STOP codons in the genetic code - UAG, UAA, and UGA. These codons signal the end of the polypeptide chain during translation.
Answer: -134 kJ
Explanation:
The balanced chemical reaction is,
The expression for enthalpy change is,
![\Delta H=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H_f%28product%29%5D-%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H_f%28reactant%29%5D)
![\Delta H=[(n_{HNO_3}\times \Delta H_{HNO_3})+(n_{NO}\times \Delta H_{NO})]-[(n_{H_2O}\times \Delta H_{H_2O})+(n_{NO_2}\times \Delta H_{NO_2})]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5B%28n_%7BHNO_3%7D%5Ctimes%20%5CDelta%20H_%7BHNO_3%7D%29%2B%28n_%7BNO%7D%5Ctimes%20%5CDelta%20H_%7BNO%7D%29%5D-%5B%28n_%7BH_2O%7D%5Ctimes%20%5CDelta%20H_%7BH_2O%7D%29%2B%28n_%7BNO_2%7D%5Ctimes%20%5CDelta%20H_%7BNO_2%7D%29%5D)
where,
n = number of moles
Now put all the given values in this expression, we get
![\Delta H=[(2\times -207)+(1\times 90)]-[(1\times -286)+(3\times 32)]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5B%282%5Ctimes%20-207%29%2B%281%5Ctimes%2090%29%5D-%5B%281%5Ctimes%20-286%29%2B%283%5Ctimes%2032%29%5D)
Therefore, the enthalpy change for this reaction is, -134 kJ
The answer is because like electric charges do not attract with each other. Ions either lack or have excess electrons in their atomic structure. Ions with a positive charge are called cations. They lack electrons in their atoms so they have to pair up with negatively charged ions, called anions, because they have excess electrons. Together, they form a compound that is neutral.
Explanation:
Let relative ratio of one isotope (62.94 u) be X
Then, relative ratio of other isotope (64.93) will be (1 - X)
Now,
(62.94)x + (64.93)(1 - x) = 63.55
1.99x = 1.38
X = 0.69
<u>Relative Abundance</u> :
(62.94 u) isotope = 69 %
(64.93 u) isotope = 31 %
