Which of the following indicates that an endothermic reaction has taken place?
Choose one answer.
a.
cooling of the surroundings

b.
release of heat and light energy

c.
a loud explosion

d.
a change in color

Question

Which of the following indicates that an endothermic reaction has taken place?
Choose one answer.
	a.
cooling of the surroundings
	
	b.
release of heat and light energy
	
	c.
a loud explosion
	
	d.
a change in color

anonymous · Answer

an endothermic reaction takes heat energy away from the surroundings. in your opinion, which of the choices is most consistent with this picture?

anonymous · Answer

A, i get it. Thanks!!

anonymous · Answer

Can you help me with another one? A carbon to carbon bond has a bond enthalpy value of 348 kJ. Which of the following must happen to form a carbon to carbon bond?
Choose one answer.
	a.
348 kJ of energy is absorbed from the surroundings
	
	b.
348 kJ of energy is released to the surroundings
	
	c.
348 kJ of energy is taken from the reactants to form the products
	
	d.
348 kJ of energy must be supplied from an external heat source

anonymous · Answer

i agree. heat energy is taken away, so the things in the surroundings jiggle a little less vigorously. this is what the book means by "cooling off".

on the second q: it takes energy to pull things apart (which make sense), so what do you think when things get bonded together? does energy come out or do we have to put energy in?

anonymous · Answer

comes out?

anonymous · Answer

So, this one is A right> Suppose two chemicals are reacted together. It takes 600 kJ of energy to break the bonds of the reactants and 950 kJ of energy are released by the formation of the products. Which statement is true about the reaction?
Choose one answer.
	a.
The reaction will give off 350 kJ of energy.
	
	b.
The reaction is endothermic.
	
	c.
The reaction will need an external energy source to proceed.
	
	d.
The reaction will have a positive ∆H value

anonymous · Answer

yep, energy comes out, and it eventually goes into the surroundings.

anonymous · Answer

i agree, it's A for the third question

anonymous · Answer

some one else said B

anonymous · Answer

well, if we just break the bonds and *stop* there without forming the product, then it's endothermic. 

but we are not stopping midway, and more energy is released at the end than was absorbed, so the reaction is exothermic overall.

anonymous · Answer

"d. The reaction will have a positive ∆H value" says the same thing as choice B. as they cannot be both true, they are both false.

anonymous · Answer

THank you for all ur help