Answer:
the first step in any stoichiometric problem is to always ensure that the chemical reaction you are dealing with is balanced,
Explanation:
The only explanation, Rutherford suggested in 1911, was that the alpha particles were being scattered by a large amount of positive charge concentrated in a very small space at the center of the gold atom.
Answer: 
Explanation: <u>Heats</u> <u>of</u> <u>formation</u> is the amount of heat necessary to create 1 mol of a compound from its molecular constituents. The basic conditions the substance is formed is at standard conditions: 1 atm and 25°C. Each compound has its own heat of formation per mol of compound (kJ/mol), but to an element is assigned a value of zero.
<u>Standard</u> <u>Enthalpy</u> <u>Change</u> is defined as the heat absorbed or released when a reaction takes place. It can be positive or negative, which means reaction is endothermic or exothermic, respectively.
Enthalpy change is calculated as the difference between the sum of heat formation of products and the sum of heat formation of the reactants:

For the reaction
2NH₃ + 3N₂O → 4N₂ + 3H₂O
2(-46.2) + 3(82.05) 4(0) + 3(-241.8)
![\Delta H^{0}=3(-241.8)-[ 2(-46.2)+3(82.05)]](https://tex.z-dn.net/?f=%5CDelta%20H%5E%7B0%7D%3D3%28-241.8%29-%5B%202%28-46.2%29%2B3%2882.05%29%5D)


<u>The standard enthalpy change for the reaction is </u>
<u> kJ</u>
An atom consist of mainly two parts, namely nucleus and electrons. In the nucleus, there are groups of protons and neutron DENSELY packed, each element has its own atomic number(number of protons) but can have different no. of neutron (isotop). within the proton and neutron, there are subatomic particles called quarks. Talking about the electrons, they move very quickly arround the nucleus and there are different energy level for electron to switch between. In chemical reaction, we are only concerning the no. of valence electrons.
Can you follow me and like me please?