Answer:
Chemical reaction involves the breaking of bonds in the reactants and formation of bonds in the products. ... If a reaction is exothermic, more energy is released when the bonds of the products are formed than it takes to break the bonds of the reactants. This is the reason for temperature change during a reaction.
Explanation:
Here are just a few everyday demonstrations that temperature changes the rate of chemical reaction: Cookies bake faster at higher temperatures. Bread dough rises more quickly in a warm place than in a cool one.
Answer:
7.1
Explanation:
equation to calculate pH is
![pH=-Log_{10}(a_{H^+})=-Log_{10}(8*10^-8) = -Log_{10}(8)-Log_{10}(10^{-8})=-0.9+8=7.1](https://tex.z-dn.net/?f=pH%3D-Log_%7B10%7D%28a_%7BH%5E%2B%7D%29%3D-Log_%7B10%7D%288%2A10%5E-8%29%20%3D%20-Log_%7B10%7D%288%29-Log_%7B10%7D%2810%5E%7B-8%7D%29%3D-0.9%2B8%3D7.1%20)
The enthalpy of reaction for the combustion of ethane 2CH₃CH₃ + 7O₂ → 4CO₂ + 6H₂O calculated from the average bond energies of the compounds is -2860 kJ/mol.
The reaction is:
2CH₃CH₃ + 7O₂ → 4CO₂ + 6H₂O (1)
The enthalpy of reaction (1) is given by:
(2)
Where:
r: is for reactants
p: is for products
The bonds of the compounds of reaction (1) are:
- 2CH₃CH₃: 2 moles of 6 C-H bonds + 2 moles of 1 C-C bond
- 7O₂: 7 moles of 1 O=O bond
- 4CO₂: 4 moles of 2 C=O bonds
- 6H₂O: 6 moles of 2 H-O bonds
Hence, the enthalpy of reaction (1) is (eq 2):
![\Delta H = \Delta H_{r} - \Delta H_{p}](https://tex.z-dn.net/?f=%20%5CDelta%20H%20%3D%20%5CDelta%20H_%7Br%7D%20-%20%5CDelta%20H_%7Bp%7D%20)
Therefore, the enthalpy of reaction for the combustion of ethane is -2860 kJ/mol.
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43.8 has 3 significant figures and 1 decimal.
<h3 /><h3>What are significant figures?</h3>
The term significant figures refer to the number of important single digits (0 through 9 inclusive) in the coefficient of an expression in scientific notation.
All zeros that occur between any two non-zero digits are significant. For example, 108.0097 contains seven significant digits. All zeros that are on the right of a decimal point and also to the left of a non-zero digit are never significant. For example, 0.00798 contained three significant digits.
Hence, 43.8 has 3 significant figures and 1 decimal.
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