If a sample of matter cannot be separated by physical means, what can be said with certainty about that sample?

A It is a pure substance.

B It is an element.

C It is a compound.

D It is a mixture.

What do you often notice after you balance a hydrocarbon combustion reaction equation? O A. Sometimes the coefficient for the oxygen molecule is not a whole number O B. Sometimes the oxygen molecules do not balance in the equation. O C.

The addition of a catalyst to a chemical reaction will have what effect? A. Increase the energy required for the reaction to take place. B. Increase the time required for the reaction to take place. C.

Why does carbon form so many organic compounds?

The molar heat of vaporization for water is 10.79 kJ/mol. How much energy must be absorbed by 100 grams of water at 100 °C in order to convert it to steam at 100 °C?

An aqueous mixture of hydrocyanic acid and ammonia has initial concentrations of 0.100 M HCN (aq) and 0.140 M NH3 (aq). At equilibrium, the CN - (aq) concentration is 0.055 M. Calculate Kc for the reaction

A chemical reaction is carried out in a closed container. The energy absorbed by the chemical reaction is 50 kJ. What is the energy liberated from the air or the walls of the container? A) 50 kJ B) 75 kJ C) 25 kJ D) 100 kJ

Draw the electron-dot structure for chclo. draw the molecule by placing the atoms on the grid and connecting them with bonds. include all lone pairs of electrons.

At stp 5.6 liters of ch4 which element contains the same number of molecules?

Is a gas that is produced by the ultraviolet radiation in the air in the vicinity of welding operations?

At what the pressure, in atmospheres, that O2, gas at 75°C has a density of 2.00 g/L