Answer:- 3. 
and 
Explanations:- An empirical formula is the simplest whole number ratio of atoms of each element present in the molecule/compound.
For example, the molecular formula of benzene is 
. The ratio of C to H in it is 6:6 that could be simplified to 1:1. So, an empirical formula of benzene is CH.
In the first pair, the ratio of C to H in first molecule is 2:4 that could be simplified to 1:2 and the empirical formula is 
. In second molecule the ratio of C to H is 6:6 and it could be simplified to 1:1. and the empirical formula is CH. Empirical formulas are different for both the molecules of first pair and so it is not the right choice.
In second pair, C to H ratio in first molecule is 1:2, so the empirical formula is . The C to H ratio for second molecule is 1:4, so the empirical formula is 
. Here also, the empirical formulas are not same and hence it is also not the right choice.
In third pair, C to H ratio in first molecule is 1:3, so the empirical formula is . In second molecule the C to H ratio is 2:6 and it is simplified to 1:3. So, the empirical formula for this one is also . Hence. this is the correct choice.
In fourth pair, first molecule empirical formula is CH. Second molecule has 2:4 that is 1:2 mole ratio of C to H and so its empirical formula is . As the empirical formulas are different, it is not the right choice.
So, the only and only correct pair is the third one. 3. and
Answer:
Explanation:
The energy of the photon can be found by using the formula
E = hf
where
E is the energy
f is the frequency
h is the Planck's constant which is
6.626 × 10-³⁴ Js
From the question we have
E = 6.626 × 10-³⁴ × 9.5 × 10¹³
We have the final answer as
Hope this helps you
4.7 M It may be wrong, but I hope it helps!
Explanation:
When you're diluting a solution, you're essentially keeping the number of moles of solute constant while changing the total volume of the solution.
Now, let's assume that you don't know the equation for dilution calculations.
In this case, you can use the molarity and volume of the concentrated solution to determine how many moles of hydrochloric acid you start with.
c
=
n
V
⇒
n
=
c
⋅
V
n
HCl
=
18 M
⋅
190
⋅
10
−
3
L
=
3.42 moles HCl
You then add water to get the total volume of the solution from
190 mL
to
730 mL
.
The number of moles of hydrochloric acid remains unchanged, which means that the molarity of the diluted solution will be
c
=
3.42 moles
730
⋅
10
−
3
L
=
4.7 M
