<span>a pure substance that can be separated into different elements by chemical means</span>
Answer:
positive
positive
Explanation:
Entropy -
In a system, the randomness is measured by the term entropy .
Randomness basically refers as a form of energy that can not be used for any work.
The change in entropy is given by amount heat per change in temperature.
- When solid is converted to gas entropy increases,
As the molecules in solid state are tightly packed and has more force of attraction between the molecules, but as it is converted to gas, the force of attraction between the molecule decreases and hence entropy increases.
So,
The particles of the substance , if are tightly held by strong force of attraction will decrease the entropy ,
And
If the particles are loosely held , the entropy will increase , i.e. , positive entropy .
Similar with solid converting to liquid , the entropy will increases , i.e. , positive entropy .
Hence ,
The correct sign of entropy for both the process is positive .
Answer: Mass of 
required to form 930 kg of iron is 1328 kg
Explanation:
To calculate the number of moles, we use the equation:
.....(1)
For iron:
Given mass of iron = 930 kg = 930000 g (1kg=1000g)
Molar mass of iron = 56 g/mol
Putting values in equation 1, we get:
The chemical equation for the production of iron follows:
By Stoichiometry of the reaction:
2 moles of iron are produced by = 1 mole of
So, 16607 moles of iron will be produced by = 
of
Now, calculating the mass of from equation 1, we get:
Mass of = 
Thus mass of required to form 930 kg of iron is 1328 kg
Answer:
Option A. The polar solvent molecule surrounds the positive sodium ions and the negative chloride ions.
Explanation:
When a salt say NaCl dissolved in water, the solvent molecules surround both the Na+ and Cl-. The Na+ are surrounded by OH- and the Cl- are surrounded by H+.
