The speed or rate of a chemical reaction is influenced by all of the following except . the concentration of the reactants.b. the temperaturec. the presence of catalysts or enzymesd. the presence or absence of carbon

The speed rate of chemical reactions is not influenced by the presence of absence of carbon.

The concentration of reactants affects the rate of reactions such that the more the concentration of these reactants, the faster the rate of reactions and vice versa.

Temperature also affects the rate of reactions such that there is a direct relationship between temperature and reaction rates, other things being equal.

Catalysts speed up the rate of reactions by providing an alternately shorter route for reactants to get to products. it lowers the activation energy of the reactants.

More on factors that affect the rate of reactions can be found here; link

option D) the presence or absence of carbon

Explanation:

Several factors affect the rate of a chemical reaction, they include:

1) temperature - some reactions increase with rise in temperature e.g Endothermic reaction

2) concentration - this increases the number of reactive particles, thus increasing reaction rate

3) catalyst - this lowers activation energy, thus bringing reaction to quick completion

However, the presence or absence of Carbon DOES NOT influence reaction rates as CARBON is neither a catalyst nor a chemically reactive specie.

According to osmotic pressure formula:
π = iCRT
when π is the osmotic pressure
i is van't Hoff factor= 2
R universal gas constant 0.0821 
T temperature in Kelvin = 298 K
C is molar concentration of solution =0.065 M
So by substitution, we will get the osmotic pressure:
∴π = 2* 0.065 * 0.0821 * 298 = 3.18 atm