Answer:
The chemical characteristics of carbon affect the characteristics of organic molecules due to its tetravalent nature. It has four valence electrons in which it shares with other elements in order to form an octet configuration.
Carbon atoms are also capable of forming double and triple bonds with other atoms. These properties help determine the functional group present and gives us a knowledge of the chemical features such as polarity, melting and boiling present in the compound.
 
        
             
        
        
        
Answer:
Explanation:
These instrument works on the analysis of the emisson spectral of light received from the star in this way. 
Think of a steel knife in your kitchen. Initially, it has this shiny silver colour that typifies it. When the knife is placed on a hot plate, it becomes hotter and begins to go red as the heating continues. If we stop the heating and pour cold water on it, the red dissapears and our knife is back to itself, although the silvery shine would be lost. This is simply how the atomic absorption spectroscopy works. When you see the hot knife you can say a couple of things about it. Different metals have their various melting point. We can compare the temperature at which our knife will melt with a standard melting point scale to know the type of metal it is made of. 
In atomic absorption spectroscopy, an atom gains energy and it becomes excited. Every atom is known to have a peculair amount of absorbant energy that cause them to excite. The more the particles in the atom, the more the energy required. When we analyse the absorbent energy of the atom, it differs from other atoms and we truly identify such an atom even if we don't know it. Most times, the energy is given off as light. 
 
        
             
        
        
        
Answer: bubbles form in boiling water
Explanation:
 
        
             
        
        
        
ZnCl2 is the chemical formula, hope this helps.
        
             
        
        
        
A reaction in which heat is evolved is an exothermic reaction while a reaction in which heat is absorbed is an endothermic reaction.
In the first case; Na2CO3 + H2SO4, we can see that this is an acid - base reaction therefore it is a neutralization reaction. Since the tube was hot after reaction, heat is given off so it is exothermic.
In the second case; NaOH + H2SO4, we can see that this is an acid - base reaction therefore it is a neutralization reaction. We are told that the tube is not hot but we don't know the initial temperature of the tube or if it was colder than it's initial temperature so we can not make any inference regarding whether the reaction is endothermic or exothermic.
Lastly, the reaction, NaCl + HC2H5OH does not occur so we mark "no reaction". We are told that the tube is not hot but we don't know the initial temperature of the tube or if it was colder than it's initial temperature so we can not make any inference regarding whether the reaction is endothermic or exothermic.
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