chem sem 1

In Haber process, ammonia is produced from nitrogen and hydrogen. Which of the following increases the value of the rate constant?

• pass the gases over iron fillings

• decreasing the volume of the reaction vessel

• Lowering the temperature of the reaction mixture

• Increasing the concentration of nitrogen and hydrogen gases.

Solid carbon dioxide or dry ice widely used as cooling agent or refrigerant. Which of the following statements best explains the reason for the use of dry ice?

• it does not leave a sticky residue

• it does not form a liquid at room temperature

• It does not vaporise at atmospheric pressure

• the gas produced does not affect the environment

The boiling point of ethanol is 78⁰C. Which of the following happens when ethanol is heated from room temperature until 78⁰C?

• the molecules expand as heat energy is absorbed

• Molecules with sufficient energy escape from the liquid

• the average kinetic energy of the molecules remains unchanged

• the vapour pressure of ethanol is less than 1 atm pressure.

When 2.40g of metal X is added to an aqueous solution containing Y²⁺ ions, 15.53g metal Y is precipitated. In this reaction, X³⁺ ions are produced. What is the relative atomic mass of X if the relative atomic mass of Y is 207?

• 27.0

• 48.0

• 55.6

• 63.5

The emission spectrum of hydrogen atom is a line spectrum because

• energy is required to excite an electron

• electrons which are unstable will radiate energy

• an excited electron has a higher energy and is not stable

• the energy of an electron in a hydrogen atom is quantised

In the context of chemical kinetics, which of the following factors does NOT affect the rate of a reaction?

• Presence of a catalyst

• Volume of the reaction vessel

• Nature of the reactants

• Temperature of the reaction mixture

What happens to the vapor pressure of a liquid as its temperature increases?

• It becomes zero

• It decreases

• It remains constant

• It increases

In a redox reaction, if substance A is oxidized, what can be inferred about substance B?

• It is a catalyst

• It is also oxidized

• It is reduced

• It remains unchanged

What can the Lyman series in the hydrogen atom spectrum be used for?

• to calculate the converging frequency

• to determine the ionisation energy for hydrogen

• to determine the bond enthalpy for hydrogen

• to determine the frequency of violet light in the visible spectrum

Among the following energy levels, which energy level has the most number of orbitals?

• n= 1

• n=2

• n=3

• n=4