Use the group numbers to determine the number of valence electrons. The Group number of a non-transition metal can be used to find the number of valence electrons in an atom of that element. The ones place of the group number is the number of valence electrons in an atom of these elements.
Among the given mediums, Vaccuum is the best thermal insulator to reduce the transfer of thermal energy by radiation as there will be no air particles which carries heat from one place to other. Hence, Option (D) will be the correct option
<h3>What is Heat radiation ?</h3>
Heat Radiation refers to the transfer of heat from a hot body to cold body directly, without heating the medium between two bodies.
Vaccum does not have any particles in it. Thus, there will be no transfer of heat through it.
The best example of it is thermous flask in which vaccuum inside thermous flask reduces the transfer of energy through it.
Hence,Among the given mediums, Vaccuum is the best thermal insulator to reduce the transfer of thermal energy by radiation as there will be no air particles which carries heat from one place to other. Thus, Option (D) will be the correct option
Learn more about radiation here ;
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Answer:
1.23 M
Explanation:
Molarity of a substance , is the number of moles present in a liter of solution .
M = n / V
M = molarity
V = volume of solution in liter ,
n = moles of solute ,
Moles is denoted by given mass divided by the molecular mass ,
Hence ,
n = w / m
n = moles ,
w = given mass ,
m = molecular mass .
From the question ,
w = given mass of NaCl = 7.2 g
As we know , the molecular mass of NaCl = 58.5 g/mol
Moles is calculated as -
n = w / m = 7.2 g / 58.5 g/mol = 0.123 mol
Molarity is calculated as -
V = 100ml = 0.1 L (since , 1 ml = 1/1000L )
M = n / V = 0.123 mol / 0.1 L = 1.23 M
Answer:
2023.04 g
Explanation:
Magnetite reacts with hydrogen to produce Iron metal and steam. Steam instead of water is produced as the reaction occurs at temperatures above the boiling point of water.
Fe₃O₄ + 4 H₂ → 3 Fe +4 H₂O
From the equation, 1 mole of Fe₃O₄ reacts with 4 moles of H₂.
69.76 grams of H₂ has the following number of moles.
Number of moles= mass/RAM
=69.76/2
=34.88 moles.
The reaction ratio of Fe₃O₄ to H₂ is 1:4
Thus number of moles of magnetite= (1×34.88)/4
=8.72 moles.
Mass= moles × molecular weight
=8.72 moles × (56×3+16×4)
=2023.04 grams
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