Answer :
An egg cooking is an endothermic reaction.
A candle burning and Plaster & water combining and becoming warm are exothermic reaction.
Salt being added to water, with no change in temperature neither endothermic nor exothermic reaction.
Explanation :
- Endothermic reaction : It is a type of reaction in which energy is absorbed in the form of heat from the surroundings.
- Exothermic reaction : It is a type of reaction in which energy is released in the form of heat from the system.
An egg cooking : In this process, the energy is absorbed in the form of heat.
A candle burning and Plaster & water combining and becoming warm : In both the process, the energy is released in the form of heat.
Salt being added to water, with no change in temperature : In this process, neither energy released nor absorbed.
PH is the test of acidity or basicity of a solution. it follows the formula:
pH = pKa + log [salt] / [acid] where NaF is the salt and HF is the acid in this case.
By literature, Ka of HF is 3.5*10^-4
<span>pKa= -log(Ka)=</span><span> 3.46 </span>
<span>pH = pKa + log [NaF / [HF] </span>
4.05 = 3.46 + log [NaF / [HF]
log [NaF / [HF]<span> = 0.59
</span>
[NaF / [HF] = 3.89
Answer:A cup of household bleach changes the color of your favorite T-shirt from purple to pink. - chemical change
Water vapor in your exhaled breath condenses in the air on a cold day.- physical change
Plants use carbon dioxide from the air to make sugar.- chemical change
Butter melts when placed in the Sun- physical change
Explanation:
A chemical change leads to the formation of a new substance and is not easily reversible. A physical change does not lead to the formation of a new substance and is easily reversible. Physical changes include condensation, melting,etc while a chemical change is a chemical reaction.
The answer is B. is the energy source of stars.
Fission is the type of nuclear energy simulated on Earth, as it is the one used to generate electricity. Fusion, on the other hand, is much more complicated to achieve because it requires extremely hot temperatures compared to fission. Fusion involves the combination of two hydrogen atoms to make helium, which releases a lot of energy. Stars such as the sun, exhibit fusion with its very hot temperature and abundant source of hydrogen.
The concept of atomic masses we can find that the correct answer is:
c) 101
The atomic mass or mass number of an element is the sum of its protons plus the neutrons that are in the atomic nucleus, the electrons are not taken into account because they have a mass much lower than the masses of protons and neutrons.
In the table they indicate that there are 46 protons and 55 neutrons, therefore
M = #_ {protons} + #_ {neutrons}
M = 46 +55
M = 101
In conclusion using the concept of atomic masses we find that the correct answer is:
c) 101
Learn more about atomic mass here:
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