The density is 181.8182 g/cm^3
Photosynthesis is the process in which green plants use sunlight to make their own food.
As the atmospheric pressure is, P = dgh
Here d is the density of the mercury,
g is gravitation = 9.8 m/s²
h is height of the column, P = 751 torr = (751 torr × 1 atm / 760 torr) (101325 Pa) (1 N/m² / 1 Pa) = 100125 N/m²
Where, 1 N = 1 Kg / ms²
Thus, P = 100125 Kg / m³. s²
Therefore, height of the mercury column, when the atmospheric pressure is 751 torr,
h = P / gd
= (100125 kg / m³. s²) / (9.8 m/s²) (13.6 × 10³ kg / m³) = 0.751 m
As, d₁h₁ = d₂h₂
Here, d₁ is the density of the non-volatile liquid = 1.20 g/ml
d₂ is the density of the mercury = 13.6 g/ml
h₂ = 0.751 m
Thus, putting the values we get,
h₁ = d₂h₂ /d₁ = 13.6 g/ml × 0.751 m / 1.20 g/ml
= 8.5 m
As a general rule of thumb molecules where metals interact with non-metals tend to form ionic bonds (because they form oppositely-charged ions), while molecules where non-metals interact with non-metals tend to form covalent bonds (because they share electrons to fill valence shells). Some of the options listed refer to large polymers of more basic units - if you can identify the basic units, you can get a sense of the kinds of bonds you're dealing with.
Starch is a polymer of glucose. Glucose is an organic molecule made of C, H, and O (all non-metals). It contains COVALENT bonds.
Graphite is a carbon polymer (sort of). Carbon is a non-metal. It contains COVALENT bonds.
Paraffin wax is a mixture of long-chain hydrocarbons (lots of carbons stuck together with some hydrogens stuck around the edges). Non-metals again. COVALENT.
Copper nitrate is a metal (copper) and a non-metal (the polyatomic ion nitrate, NO3-). Therefore, copper nitrate as a whole is IONIC (be careful though - the N and O within the nitrate ion are both non-metals and so are bonded covalently, but they ultimately form an ion that is capable of forming ionic bonds with metals).
Iron oxide is a general term for some combination of iron (a metal) and oxygen (a non-metal). Regardless of the specific combination, the interaction is IONIC.
Sucrose is formed when glucose interacts with another sugar, fructose. Again, only C, H, and O are involved, so the molecule is COVALENT.
Calcium carbonate is similar to the copper nitrate situation - you have a metal (calcium) and a non-metal (carbonate) interacting though an IONIC bond. As with nitrate, carbonate (CO3[2-]) is itself a polyatomic anion containing covalent bonds between the C and O's, but forms ionic bonds because it is ultimately an ion.
Happy to clarify anything if need be!