February chemistry exam for grade 10 second semester

In these two solutions :

1)KCl_(s) + 10H₂O_(l) → KCl_(aq) ΔH₁= (x) KJ/mol

2)KCl_(s) + 80H₂O_(l) → KCl_(aq) ΔH₂= (Y) KJ/mol

Which of the following represents ΔH^°_dil of potassium chloride?

• (X+Y)KJ

• (X-Y)KJ

• -(X+Y)KJ

• (Y-X)KJ

If the dissociation energy of ammonium nitrate salt in water equals 150 KJ,

its hydration energy equals 120 KJ and

the separation energy of water equals 100 KJ.

What is the type of solution of this salt? What is its ΔH?

• Exothermic /- 130 KJ

• Endothermic / + 170 KJ

• Exothermic / - 170 KJ

• Endothermic / + 130 KJ

The intact egg is an example for the ...........

• Closed system

• Open system

• Isolated system

• Closed or open system

What is the quantity of heat required to raise the temperature of 1500 g of oil from 20°C to 180°C,

knowing that the specific heat of the oil used is 1970 J/Kg. °C?

• 568.9 KJ

• 472.8 KJ

• 681.3 KJ

• 743.2 KJ

Which of the following represents the closed system as the time passes?

• The energy remains constant but the mass changes

• Both the temperature and the mass change

• The mass remains constant but energy changes

• both the temperature and the mass dont change

Which of the following represents the closed system as the time passes?

• The energy remains constant but the mass changes

• Both the temperature and the mass change

• The mass remains constant but energy changes

• both the temperature and the mass dont change

In terms of the thermochemical equation :

CH_4(g)→C_(s) + 4H_(g) ΔH= +1648 KJ/mol

What is the energy of the bond (C-H)?

• +412 KJ/mol

• +329.6 KJ/mol

• +1648 KJ/mol

• +6592 KJ/mol

From the opposite energy diagram:

What is the value of the change in heat content of the reaction:

C + D → A + B

• -225 KJ/mol

• +225 KJ/mol

• +75 KJ/mol

• -75 KJ/mol

From the equation :

2C_(s) +2H_2(g)+52.3 KJ →C₂H_4(g)

it can be concluded that ...........

• the medium acquires heat

• heat transfers from the surrounding to the system

• the system loses heat

• heat transfers from the system to the surrounding

Two pieces of equal masses and the same temperature are heated for an equal period of time by the same heat source , if u know that the first piece of metal has a specific heat equals 0.385 KJ/g.°C and the second piece of metal has a specific heat equals 0.444 KJ/g.°C

Which one its temperature rises more?

• the first piece as it has a lower specific heat

• the second as it has a higher specific heat

• the first as it takes longer time to raise its temperature

• the second as it takes longer time to raise its temperature