Which of the following are properties of hydrocarbons? (a) hydrophilic, good source of stored energy, nonpolar.(b) hydrophilic, polar, consisting primarily of carbon, hydrogen.(c) hydrophobic, containing many hydroxide groups, polar.(d) hydrophobic, nonpolar, good source of stored energy

the correct answer is (D) hydrophobic, nonpolar, good source of stored energy,

Explanation:

Hydrophobic literally means the 'fear of water, . Hydrocarbons are compounds that are composed of hydrogen and carbon molecules. The hydrophobic effect is caused by the hydrocarbons tendency to repel water molecules. The molecular structure of hydrocarbons creates a cage that doesn't allow water to pass through them.

The molecules of hydrocarbons are nonpolar because the atoms in the molecules have similar electronegativities.

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen. They make good fuels because their covalent bonds store a large amount of energy, which is released when the molecules are burned ( for example, when they react with oxygen to form carbon dioxide and water).

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol