A reaction is exothermic if Δ<em>H</em> (or 
in some textbooks) is negative:
- H₂ + Br → 2 HBr, ΔH < 0.
- CH₄ + 2 O₂ → CO₂ + 2 H₂O, ΔH < 0.
A reaction is endothermic if Δ<em>H</em> is positive:
- 2 NH₃ → N₂ + 3 H₂, ΔH > 0.
- 2 HCl → H₂ + Cl₂ ΔH > 0.
<h3>Explanation</h3>
The enthalpy of a system is the sum of its internal energy. ΔH < 0 indicates that the reactants lose internal energy in the reaction. Energy conserves, and those internal energies must have converted to some other form of energy. They typically end up as thermal energy. The reaction will release heat since it is exothermic.
Similarly, ΔH > 0 indicates that the reactants gains internal energy in the reaction. Energy conserves. As a result, the reaction must have gained energy from its surroundings. The reaction will be endothermic since it absorbs heat.
Answer:
En total son 8 modelos, en la explicación los nombraremos por orden de antigüedad.
Explanation:
Modelo atómico de Demócrito (450 a.C.)
Modelo atómico de Dalton (1803 d.C.)
Modelo atómico de Lewis (1902 d.C.)
Modelo atómico de Thomson (1904 d.C.)
Modelo atómico de Rutherford (1911 d.C.)
Modelo atómico de Bohr (1913 d.C.)
Modelo atómico de Sommerfeld (1916 d.C.)
Modelo atómico de Schrödinger (1926 d.C.)
Answer
A *single covalent bond* is formed by sharing one pair of valence electrons.They are less reactive comparatviely and have a high bond length
A *double covalent bond* is formed by sharing two pairs of valence electrons.They are moderately reactive and have moderate bond length.
A *triple covalent bond* is formed by sharing three pairs of valence electrons.They are highly reactive and have a low bond length.
NH₄Cl → NH₄⁺ + Cl⁻
NH₄⁺ (the ammonium cation)
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<h2 /><h2 /><h2><u>Solution </u><u>3</u><u> Is The Most Concentrated</u></h2>
<h3>S1:</h3>
M = m/v
= 100ml ÷ 2 spoons × 100%
= - 5,000 μg/ppb³
= <u>50% Diluted</u>
<h3>S2:</h3>
M = m/v
= 200ml ÷ 5 spoons × 100%
= - 4,000 μg/ppb³
= <u>40% Diluted</u>
<h3>S3:</h3>
M = m/v
= 300ml ÷ 6 spoons × 100%
= - 5,000 μg/ppb³
= <u>50% Diluted</u>
<h3>S4: </h3>
M = m/v
= 600ml ÷ 8 spoons × 100%
= - 75,000 μg/ppb³
= <u>75% Diluted</u>
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