Answer:
The r.a.m. value is used to determine how many isotopes an element has.
Explanation:
 
        
             
        
        
        
Answer:
H+ and NO3- ions
Explanation:
The Pb²+ ions react with the SO4²‐ ions to form a solid precipitate, i.e. they bond together and undergo a phase change;
On the contrary, the H+ and NO3- ions are aqueous ions before the reaction and the same after the reaction, i.e. they don't change;
Hence, the H+ and NO3- ions are spectator ions
The way to do this type of question is to consider what changes and what doesn't, look at phase changes and oxidation state changes 
 
        
             
        
        
        
Answer:
A Horizon - The layer called topsoil; it is found below the O horizon and above the E horizon. Seeds germinate and plant roots grow in this dark-colored layer. It is made up of humus (decomposed organic matter) mixed with mineral particles.
 
        
             
        
        
        
A grey coloured rock with amphibole and intermediate plagioclase like an andesine would classify as an intermediate rock by Bowen's Reaction Series and by the classification of igneous rocks would probably be like a diorite which is intermediate between a gabbro and a granite. A diorite essentially has no quartz but has the silicates amphibole (like hornblende), mica perhaps a little pyroxene and andesine plagioclase.