Answer:
The answer is: (a) positive; (b) negative.
Explanation:
The change in enthalpy (ΔH) of a reaction is the amount of energy absorbed or released during a chemical reaction carried out at constant pressure.
a) In an endothermic chemical reaction, heat energy is absorbed by the system from the surrounding. Therefore, the sign of enthalpy change for an endothermic process is positive, ΔH= positive.
b) In an exothermic chemical reaction, heat energy is released by the system into the surrounding. Therefore, the sign of enthalpy change for an exothermic process is negative, ΔH= negative.
Answer:
89°C
Explanation:
Combined Gas Law (P₁V₁)/T₁ = (P₂V₂)/T₂
(1.25 atm)(450 mL)/(65°C) = (0.89 atm)(865 mL)/T₂
8.653846154 = 769.85/T₂
T₂ = 769.85/8.653846154
T₂ = 88.96044444 = 89°C
Answer:
There are 0,011 moles of hydrogen gas.
Explanation:
We use the ideal gas formula, with the constant R = 0.082 l atm / K mol. The STP conditions are : 1 atm pressure and 273 K temperature. Solve for the formula, n (number of moles):
PV=nRT ---> n= (PV)/(RT)
n= (1 atm x 0,25 L)/ (0,082 l atm/ K mol x 273 K)
<em>n= 0,011 mol</em>
Answer:
1) Covalent bond, in chemistry, the interatomic linkage that results from the sharing of an electron pair between two atoms. The binding arises from the electrostatic attraction of their nuclei for the same electrons.
2)A molecule is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up of atoms that are held together by chemical bonds. These bonds form as a result of the sharing or exchange of electrons among atoms.
3)Hydrogen (H2), oxygen (O2), and chlorine (Cl2) molecules, for example, each contains two atoms. Another form of oxygen, ozone (O3), has three atoms, and sulfur (S8) has eight atoms. All elemental molecules are made of atoms of a single element.
Explanation:
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