<span>The </span>standard enthalpy of formation<span> <span>is defined as the change in </span></span>enthalpy<span> <span>when one mole of a substance in the </span></span>standard<span> <span>state (1 atm of pressure and temperature of 298.15
K) is </span></span>formed<span> <span>from its
pure elements under the same conditions.</span></span>
The answer to the chemistry question above would be pure substance. Bromine is classified as a pure substance because only the element is present and there are no other substances added or mixed with it. It is also not a compound because it does not come with another element.
The value of pka for 
in an aqueous solution is 9.2.
<h3>What is Kb?</h3>
Kb denotes the base dissociation constant.
pKa + pKb =14 at 25 degree celcius.
pKa + 4.8 =14
pKa = 9.2
pKb is the negative base-10 logarithm of the base dissociation constant (Kb) of a solution.
It is used to determine the strength of a base or alkaline solution.
The value of pka for in an aqueous solution is 9.2.
Learn more about pka here:
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Answer:
- The main idea behind MADs is that they use the principle that metallic objects (submarines) interfere in the magnetic lines of Earth forces. And this equipment detects this anomaly.
- Submarines can be detected by using MADs
- The history of MAD development
In 1917 the interest in the detection of submarines started with the study hydrophones. Then in 1918, the U.S. considered to use the magnetism in this area but it did not result to be practical as it had a limited detection range.
Then by 1941 in Britain and in U.S. developed magnetic detection devices to measure Earth’s magnetic field, so after that in 1943 MADs were installed in ASW aircrafts.
Due to the limited range and its lack of ability to detect the magnetic variance from different sources, MAD started to be used in combination with sonobuoys. This combination allowed an aircraft to localize submarines with the confirmation of sonobuoys.
Explanation:
MADs are Magnetic Anomaly Detectors. Their function is to detect anomaly in the Earth’s magnetic field caused by submarines.
Submarines are made of ferrous metal which contain domains that are tiny magnets form of iron molecules. This material creates a disturbance that can be detected in the magnetic field.
<h3>
Answer:</h3>
2.5 moles
<h3>
Explanation:</h3>
<u>We are given;</u>
We are required to determine the number of moles of sodium.
- We know that, 1 mole of an element contains a number of atoms equivalent to the Avogadro's number, 6.022 × 10^23.
- That is, 1 mole of an element = 6.022 × 10^23 atoms.
Therefore;
1 mole of sodium contains 6.022 × 10^23 atoms
To get the number of moles;
= Number of atoms ÷ Avogadro's number
= 1.5 × 10^24 atoms ÷ 6.022 × 10^23 atoms/mol
= 2.49 moles
= 2.5 moles
Therefore, 2.5 moles of sodium contains 1.50 × 10^24 sodium atoms
