Answer:
The equilibrium shifts to the left, and the concentration of Ba2+(aq) decreases
Explanation:
Whenever a solution of an ionic substance comes into contact with another ionic compound with which it shares a common ion, the solubility of the ionic substance in solution decreases significantly.
In this case, both BaSO4 and Na2SO4 both possess the SO4^2- anion. Hence SO4^2- anion is the common ion. Given the equilibrium;
BaSO4(s) <—> Ba2+ (aq) + SO4 2- (aq), addition of Na2SO4 will decrease the solubility of BaSO4 due to the presence of a common SO4^2- anion compared to pure water.
This implies that the equilibrium will shift to the left, (more undissoctiated BaSO4) hence decreasing the Ba^2+(aq) concentration.
Answer: balanced chemical equation: 
Net ionic equation :
Explanation:
A double displacement reaction is one in which exchange of ions take place. The salts which are soluble in water are designated by symbol (aq) and those which are insoluble in water and remain in solid form are represented by (s) after their chemical formulas.
The balanced chemical equation is:

Spectator ions are defined as the ions which does not get involved in a chemical equation or they are ions which are found on both the sides of the chemical reaction present in ionic form.
The ions which are present on both the sides of the equation are sodium and nitrate ions and hence are not involved in net ionic equation.
Hence, the net ionic equation is
Answer is: volume will be 3.97 liters.
Boyle's Law: the pressure volume law - volume of a given amount of gas held varies inversely with the applied pressure when the temperature and mass are constant.
p₁V₁ = p₂V₂.
p₁ = 755 torr.
V₁ = 5.00 l.
p₂ = 1.25 atm · 760 torr/atm.
p₂ = 950 torr.
755 torr · 5 l = 950 torr · V₂.
V₂ = 755 torr · 5 l / 950 torr.
V₂ = 3.97 l.
When pressure goes up, volume goes down.
When volume goes up, pressure goes down.
The density is 4 g/cm³ or 4000 kg/m³.
Density = mass/volume = 12 g/3 cm³ = 4 g/cm³
The measurement of 4 g/cm³ is already in <em>SI units</em>.
In SI <em>bas</em>e units,
Density = (4 g/1 cm³) × (1 kg/1000 g) × (100 cm/1 m)³ = 4000 kg/m³