An element is a pure substance which means it cannot be broken down by any means.
Answer:

Explanation:
The products of this reaction are given by:

Firstly, dichromate anion becomes chromium(III) cation, let's write this change:

The following steps should be taken:
- balance the main element, chromium: multiply the right side by 2 to get 2 chromium species on both side:

- balance oxygen atoms by adding 7 water molecules on the right:

- balance the hydrogen atoms by adding 14 protons on the left:

- balance the charge (the total net charge on the left is 12+, on the right we have 6+, so 6 electrons are needed on the left):

Similarly, tin(II) cation becomes tin(IV) cation:

Now that we have the two half-equations, multiply the second one by 3, so that it also has 6 electrons that will be cancelled out upon addition of the two half-equations:


Add them together:

Adding the ions spectators:

What do you need help with? Can you specify?
Volume Ba(OH)2 = 23.4 mL in liters :
23.4 / 1000 => 0.0234 L
Molarity Ba(OH)2 = 0.65 M
Volume HNO3 = 42.5 mL in liters:
42.5 / 1000 => 0.0425 L
number of moles Ba(OH)2 :
n = M x V
n = 0.65 x 0.0234
n = 0.01521 moles of Ba(OH)2
Mole ratio :
<span>Ba(OH)2 + 2 HNO3 = Ba(NO3)2 + 2 H2O
</span>
1 mole Ba(OH)2 ---------------- 2 moles HNO3
0.01521 moles ----------------- moles HNO3
moles HNO3 = 0.01521 x 2 / 1
moles HNO3 = 0.03042 / 1
= 0.03042 moles HNO3
Therefore:
M ( HNO3 ) = n / volume ( HNO3 )
M ( HNO3 ) = 0.03042 / 0.0425
M ( HNO3 ) = 0.715 M