Answer:
oxygen is an element because it is a pure substance which cannot be split into simpler substances by chemical means 
 
        
             
        
        
        
The central vacuole stores materials, wastes, and helps give the plant structure and support.
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Answer:
La tabla periódica de moseley fue una manera de dar solución a esta problemática, ya que nos permite tener a la mano todos los elementos que se han descubierto hasta la actualidad y sus propiedades químicas más resaltantes.
A continuación se Describe una linea del tiempo de la creación de la tabla periodica:
1820 -  se crean las tríadas de Dobereiner.  
1863 - se crea el cilindro de chancourtois.  
1864 - se crean las octavas de newlands.  
1869 - se crea el primer prototipo de la tabla periódica.  
1914 - se fórmula la ley periódica moderna por Moseley.
Explanation:
 
        
             
        
        
        
Answer:  
 
Explanation:
Moles of   = 1 mole
 = 1 mole
Moles of   = 1 mole
 = 1 mole
Volume of solution = 1 L
Initial concentration of  = 1 M
 = 1 M
Initial concentration of  = 1 M
 = 1 M
The given balanced equilibrium reaction is,
                   
Initial conc.          1 M                      0M          1 M
 At eqm. conc.     (1-2x) M              (2x) M       (1+x) M
The expression for equilibrium constant for this reaction will be,
![K_c=\frac{[NO]^2[Cl_2]}{[NOCl]^2}](https://tex.z-dn.net/?f=K_c%3D%5Cfrac%7B%5BNO%5D%5E2%5BCl_2%5D%7D%7B%5BNOCl%5D%5E2%7D)
The  =
= 
Now put all the given values in this expression, we get :

By solving the term 'x', we get :

Concentration of  at equilibrium= (2x) M  =
 at equilibrium= (2x) M  =   
 
 
        
             
        
        
        
Pb(NO₃)₂ + (NH₄)₂CO₃ → PbCO₃ + 2 NH₄NO₃
Explanation:
Reaction of lead (II) nitrate with ammonium carbonate will produce lead (II) carbonate and ammonium nitrate.
The balanced chemical equation is:
Pb(NO₃)₂ + (NH₄)₂CO₃ → PbCO₃ + 2 NH₄NO₃
To balance the chemical equation the number of atoms of each element  
entering the reaction have to be equal to the number of atoms of each  
element leaving the reaction, in order to conserve the mass.
Learn more about:
balancing chemical reactions
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