Answer:
w = -531 kJ
1. Work was done by the system.
Explanation:
Step 1: Given data
- Heat gained by the system (q): 687 kJ (By convention, when the system absorbs heat, q > 0).
- Change in the internal energy of the system (ΔU°): 156 kJ
Step 2: Calculate the work done (w)
We will use the following expression.
ΔU° = q + w
w = ΔU° - q
w = 156 kJ - 687 kJ
w = -531 kJ
By convention, when w < 0, work is done by the system on the surroundings.
A Chemical change is any form of chemical reaction changing the state of the matter involved. When you fry an egg, you are making a reaction between the heat and the chemicals that make up the egg. Therefore once you have fried that egg, you have completed a chemical reaction. This is why it's a chemical change when you fry an egg.
Given the fact that we are seeing a rise in the temperature of the globe, the artic animals in that ecosystem must adapt by a reduction in the rate of metabolism.
<h3>What is global warming?</h3>
Several evidences continue to emerge that the temperature of the earth have continued to increase and this is largely due to the fact that since the turn of the twentieth century and the rise of industrialization, there have been a rise in the emission of the carbon dioxide and other green house gases into the environment. As a result of this, the temperature of the earth has continued to rise steadily leading to the melting of the ice cover and the destruction of ecosystems that are found around the artic regions of the earth.
Now, we know that an organism is able to adapt to the changes that occur in its habitat by being able to alter some of its structure and function.
Given that the organisms that live in the artic are adapted to cold regions and low temperatures, the metabolic rate of the organisms is high in order to produce heat.
As a result of the rise in global temperatures, the organisms would have to reduce their rate of metabolism.
Learn more about global warming:brainly.com/question/12908180
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Pb(NO₃)₂ ⇒limiting reactant
moles PbI₂ = 1.36 x 10⁻³
% yield = 87.72%
<h3>Further explanation</h3>
Given
Reaction(unbalanced)
Pb(NO₃)₂(s) + NaI(aq) → PbI₂(s) + NaNO₃(aq)
Required
- moles of PbI₂
- Limiting reactant
- % yield
Solution
Balanced equation :
Pb(NO₃)₂(s) + 2NaI(aq) → PbI₂(s) + 2NaNO₃(aq)
mol Pb(NO₃)₂ :
= 0.45 : 331 g/mol
= 1.36 x 10⁻³
mol NaI :
= 250 ml x 0.25 M
= 0.0625
Limiting reactant (mol : coefficient)
Pb(NO₃)₂ : 1.36 x 10⁻³ : 1 = 1.36 x 10⁻³
NaI : 0.0625 : 2 = 0.03125
Pb(NO₃)₂ ⇒limiting reactant(smaller ratio)
moles PbI₂ = moles Pb(NO₃)₂ = 1.36 x 10⁻³(mol ratio 1 : 1)
Mass of PbI₂ :
= mol x MW
= 1.36 x 10⁻³ x 461,01 g/mol
= 0.627 g
% yield = 0.55/0.627 x 100% = 87.72%
