An object floats in liquid of density 1.2×10kgm/3 with one quarter of its volume

900 kg/m³

Explanation:

There are two forces on the object: weight and buoyancy.

Newton's second law:

∑F = ma

B − W = 0

B = W

Weight is mass times gravity:

W = m₀ g

Mass is density times volume:

W = ρ₀ V₀ g

Buoyancy force is equal to the weight of displaced fluid:

B = ρ V g

Therefore:

ρ V g = ρ₀ V₀ g

ρ V = ρ₀ V₀

ρ₀ = ρ V / V₀

One quarter of the object's volume is above the liquid, which means three quarters of its volume is below the surface.

Given that V = ¾ V₀ and ρ = 1200 kg/m³:

ρ₀ = 1200 (3/4)

ρ₀ = 900 kg/m³

To balance the equation, we need to write how many elements is on each side of the equation. 

Since the coefficient will apply to the whole compound (all the elements) we need to determine how many is on the reactants side. 

Na=2 
O=6
N=2   

Since their is already a subscript of 3, we can already conclude that we multiply 2*3=6. Therefore, our answer would be 2.

To balance the equation, we need to place a coefficient of 2 in front of NaNO3.