The answer is B. Temperate.
Explanation:
A chemical reaction is defined as the reaction in which bonds between the reactants either break or form which leads to the formation of a new substance.
For example, 
So, when we drop a sodium metal into water then it produces a frizzing sound which shows the metal is reacting with water.
We know that when two aqueous solutions chemically react with each other then it may lead to the formation of an insoluble substance which is known as precipitate.
This means that formation of a precipitate is also a chemical reaction.
Thus, we can conclude that following are the statements which show evidence for a chemical reaction.
- Dropping sodium metal into water produces fizzing.
- Mixing two aqueous solutions produces a precipitate.
Answer:
It's not correct. For balancing, we need to put the coefficients in the molecule, not in the athom. Because if you do this, you're creating another molecule, instead of a balacing, for which the reaction may not happen - but anyway, it would be another reaction.
The correct balacing is:
2NaOH + 1H2S → 1Na2S + 2H2O
Explanation:
Look: Na2OH does not even exist. OH has only one free link, so he can't - in normal conditions - make another one with any athom. That's why we should write 2NaOH instead of Na2OH. The first means "2 mols of NaOH".
Answer:
2100 kPa
Explanation:
The temperature is constant, so the only variables are pressure and volume.
We can use Boyle’s Law.
p₁V₁ = p₂V₂ Divide both sides of the equation by V₂
p₂ = p₁ × V₁/V₂
p₁ = 485 kPa; V₁ = 648 mL
p₂ = ?; V₂ = 0.15 L = 150 mL Calculate p₂
p₂ = 485 × 648/150
p₂ = 2100 kPa