Answer:
half lives passed=5
given sample=90g
sample left=2.8125g
Explanation:
no. of half lives=total time/half life
no.=19days/3.8days
no.=5 days
after 5 half lives sample left=2.8125g
Answer: Option (b) is the correct answer.
Explanation:
When useful energy is conserved then this conservation is known as energy conservation.
For example, when lights of a room are switched on where no one is sitting then on switching off the lights we are conserving wastage of electricity.
Thus, we can conclude that out of the given options, the statement energy resources can be conserved by turning off lights when they are not in use is true.
Answer:- 30 moles of oxygen are required if 12 moles of 
are consumed.
Solution:- The given balanced equation is:
From this balanced equation, there is 2:5 mol ratio between and 
.
We are asked to calculate the moles of required to react with 12 moles of .
It's a mol to mol conversion and the set up for this would be as:
= 
So, 30 moles of oxygen are required to react with 12 moles of .
Answer:
Expansion: increase in size Contraction: decrease in size
Explanation:
Answer:
Option A. H₂O
Explanation:
PCl3 + 3H2O → H3PO3 + 3HCI
From the equation,
We can see clearly that for every 3moles of H2O, 1mole of PbCl3 is needed. This clearly indicates that H2O is the limiting reactant. This can further be proved by doing the following:
From the equation,
1mole of PbCl3 required 3moles of H20.
Therefore, 7moles of PbCl3 will require = 7x3 = 21moles of H2O. This amount(i.e 21moles) of H20 is far greater than what was given (i.e 5moles of H2O) from the question.
Now let us consider the reverse case as follows:
From the equation,
1mole of PbCl3 required 3moles of H20.
Therefore, Xmol of PbCl3 will require 5moles of H2O i.e
Xmol of PbCl3 = 5/3 = 1.67moles
This amount(i.e 1.67moles of PbCl3) obtained is smaller than what was given (i.e 7moles of PbCl3) from the question.
This shows that PbCl3 is excess and H20 is the limiting reactant
