Answer:

Explanation:
Given that,
The dimensions of the board is 5.54 cm x 10.6 cm X 199 cm.
The mass of the board is 28.6 kg.
Since, 1 kg = 1000 grams
28.6 kg = 28.6 × 1000 g = 28600 grams
Density = mass/volume
So,

So, the density of a board is
.
Answer:
The correct answer will be "
".
Explanation:
We have:
Moles of solute (Na₂Co₃) = 
= 
= 
Now,
The volume of the solution will be:
⇒ 
∴ 
The formula to find the concentration will be:
⇒ 
On substituting the given values, we get
⇒ 
⇒ 