00:03
Hello, in this question we are given this chemical reaction and we're told that the delta h is positive 221.
00:12
Therefore our first question wants to know is this endothermic or exothermic? well by convention it is it has been determined that a positive of delta h means that energy has gone into the system.
00:30
So we have added 221 joules or kilojoules rather per mole to the system.
00:41
Therefore if energy is going in due to that positive exponent or that positive value it must be endothermic.
00:58
Energy is a reactant.
01:04
The reverse is also true if delta h is negative then it means that it's exothermic and energy is being given off.
01:10
But in this one our value is positive so it is endothermic.
01:20
All right for letter b what we want to do is calculate how much energy is released or absorbed if we start with 12 .5 grams of manganese.
01:38
Okay well let's look at what we know.
01:39
We know we're working with manganese so we know that we can use its molar mass to convert to moles.
01:46
And we also see since we have the 221 kilojoules in the equation we can say that for every mole of manganese 221 kilojoules of energy are required.
02:08
Of course that's a positive value...