Answer:
the reactivity and the valence electrons
Explanation:
the reactivity of the elements would have played a significant role in why such elements were grouped together. the number of valence electrons dictates how reactive an element is - the less valence electrons the more reactive it is. the column, group 1 in which these elements are put together in, show that each of the elements have 1 valence electrons and are therefore reactive.
you can go on to further explain what valence electrons are, explain what the group numbers are associated with the valence electrons and how valence electrons effect reactivity. further this, talk about how the three elements have the same number of valence electrons and therefore were grouped together
<u>Answer:</u> The net ionic equation for the given reaction is 
<u>Explanation:</u>
Net ionic equation of any reaction does not include any spectator ions.
Spectator ions are the ions which do not get involved in a chemical equation. It is also defined as the ions that are found on both the sides of the chemical reaction when it is present in ionic form.
The chemical equation for the reaction of hydrochloric acid and potassium sulfite is given as:

Ionic form of the above equation follows:

As, potassium and chloride ions are present on both the sides of the reaction, thus, it will not be present in the net ionic equation.
The net ionic equation for the above reaction follows:

Hence, the net ionic equation for the given reaction is written above.
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Answer: The molar enthalpy of formation for paraffin wax is -2460.5 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_{CO_2}\times \Delta H_{CO_2})+(n_{H_2O}\times \Delta H_{H_2O})]-[(n_{O_2}\times \Delta H_{O_2})+(n_{C_{25}H_{52}}\times \Delta H_{C_{25}H_{52}})]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5B%28n_%7BCO_2%7D%5Ctimes%20%5CDelta%20H_%7BCO_2%7D%29%2B%28n_%7BH_2O%7D%5Ctimes%20%5CDelta%20H_%7BH_2O%7D%29%5D-%5B%28n_%7BO_2%7D%5Ctimes%20%5CDelta%20H_%7BO_2%7D%29%2B%28n_%7BC_%7B25%7DH_%7B52%7D%7D%5Ctimes%20%5CDelta%20H_%7BC_%7B25%7DH_%7B52%7D%7D%29%5D)
where,
n = number of moles
(as heat of formation of substances in their standard state is zero
Now put all the given values in this expression, we get
![-14800=[(25\times -393.5)+(26\times -285.5)]-[(38\times 0)+(1\times \Delta H_{C_{25}H_{52}})]](https://tex.z-dn.net/?f=-14800%3D%5B%2825%5Ctimes%20-393.5%29%2B%2826%5Ctimes%20-285.5%29%5D-%5B%2838%5Ctimes%200%29%2B%281%5Ctimes%20%5CDelta%20H_%7BC_%7B25%7DH_%7B52%7D%7D%29%5D)

Therefore, the molar enthalpy of formation for paraffin wax is -2460.5 kJ
Answer:
10.5 dm3 O2
0.94 moles de MgO
Explanation:
La pregunta dice explícitamente que el magnesio es puro en un 90%.
Por lo tanto, masa de magnesio puro = 90/100 * 25G = 22,5 g
Número de moles de Mg = 22,5g / 24g/mol = 0,94 moles de Mg
La ecuación de reacción es;
2Mg (s) + O2 (g) ------> 2MgO (s)
Si 2 moles de Mg reaccionan con 1 moles de O2
0.94 moles de Mg reacciona con 0.94 * 1/2 = 0.47 moles de O2
Si 1 mol de O2 ocupa 22,4 dm3
0.47 moles de O2 ocupan 0.47 * 22.4 / 1 = 10.5 dm3
También;
2 moles de Mg producen 2 moles de MgO
Entonces, 0.94 moles de Mg producen 0.94 moles de MgO