Answer:
A. 1 = 3 - 2
Explanation:
What defines an expression?
expression - An expression is a sentence with a minimum of two numbers and at least one math operation. This math operation can be addition, subtraction, multiplication, and division.
So if we look at the letter options we can see that A is the best choice.
Molality is defined as 1 mole of a solute in 1 kg of solvent.
Molality=

Number of moles of solute, n=

Given mass of the nitrobenzene=0.2 g
Molar mass of the substance= 123.06 g mol⁻¹
Number of moles of nitrobenzene,

Number of moles of nitrobenzene, n= 0.0016 mol
Mass of 10.9 g of naphthalene in kg=0.0109

Molality= 0.146 m
Answer:
437.5 kg of first solution and 812.5 kg of second solution should be mixed to get desired solution.
Explanation:
Let the mass of the first solution be x and second solution be y.
Amount solution required = 1250 kg
x + y = 1250 kg....[1]
Percentage of ethanol in required solution = 12% of 1250 kg
Percentage of ethanol in solution-1 = 5% of x
Percentage of ethanol in required solution = 25% of y
5% of x + 25% of y =12% of 1250 kg

x + 5y = 3000 kg...[2]
Solving [1] and [2] we :
x = 437.5 kg , y = 812.5 kg
437.5 kg of first solution and 812.5 kg of second solution should be mixed to get desired solution.
“Water” is the best thermal insulator.
Option: B
<u>Explanation</u>:
“Thermal insulators” are the materials which do not allow heat to transfer. “Water” is the substance which does not transfer heat. Hence, the “water” is the best “thermal insulator”. Water is the bad conductor of thermal heat. Water has “low thermal conductivity” than other substances, so this acts as an insulator as long as it is not traveled from one place to another. Heat is transferred when a “hot object collides” with “the cold objects”. The “thermal conductivity” of “water” is 0.6 W/m K.