Which of the following is an application of law of conservation of energy? …

• The total energy of an isolated system which contains ice remains the same even when the ice is turned to water

•   Hydrogen gas and oxygen gas react together to form water with releasing thermal energy

•   In photosynthesis, light energy converts into chemical energy

• Reaction of magnesium with oxygen is accompanied by absorbing thermal energy.

Which of the following statements represents a closed system? .........

• The in coming mass = the outgoing mass from the system.

• Matter does not transfer either to or from the system

• Incoming matter in the system might be more or less than the outgoing matter.

• It does not exchange either heat or work with its surrounding.

What is the system which contains a constant mass of matter and its boundaries do not allow the passage of matter ? ...............

• Equilibrium system

• Open system.

• Closed system.

• Thermally equilibrium system.

What is the quantity of energy which is equivalent to 50 kJ? ...

• 0.05 J

• 500 J

•   5 x 10³ J

•    5 x 10⁴ J

 If the temperature of a substance is doubled as well as its mass, its specific heat will be...

•   decreased to quarter

•   constant

•   increased to double

• increased to four times

  In the following reaction:

2Na2O2(s)+ 2H2O(l) → 4NaOH(s)+O2(g) ∆H =-126 kJ

What is the quantity of heat released by producing 2 mol of ?

• +252 kJ

• +63 kJ

• +3.9 kJ

• +78 kJ

   In the reaction:

2H2O(l)→2H2O(l)+O2(g) ∆H =-196 kJ

What is the change in the enthalpy of the decomposition of 0.34 g of hydrogen peroxide                                                                                                                                              [H=1, O=16]

•   -0.98 kJ

• -1.96 kJ

• -196 kJ

• -98 kJ

  Nitrogen reacts with oxygen according to the following thermochemical equation:

N2(g)+2O2(g)→2NO2(g) ∆H = +66 kJ

What is the change in enthalpy on mixing 2 mol of nitrogen with 2 mol of oxygen?

• +132 kJ

•   +66 kJ

•   +33 kJ

•   +16.5 kJ

Which of the following statements represents the type of the chemical reaction which happens when a match head is rubbed against a rough surface?

• Endothermic reaction due to using energy on rubbing the match head.

•    Endothermic reaction due to releasing energy on burning the wooden match.

• Exothermic reaction due to using energy on rubbing the match head.

•   Exothermic reaction due to releasing energy on rubbing the wooden match.

Which of the following statements represents correctly the endothermic reaction?

• The bonds 1 in the products molecules are stronger than those in reactants molecules

•   The bonds j in the reactants molecules are stronger than those in products molecules

•   The heat content of the products is lower than that of the reactants.

• It occurs spontaneously in low temperatures.