S1-Q3-U4-lesson 1- till bonds energies

According to the following reaction . How much energy is needed to decompose 3.2 moles of calcium nitrate?

• 369 KJ

• 738 KJ

• 590.4 KJ

• 922.5 KJ

The value of Δ𝐻 when liquid water freezes to solid water is −6.01 kJ/mol. What is the value of Δ𝐻 when solid water melts to liquid water ?

• -6.01

• +6.01

• +12.02

• -12.04

Which of these statements does not describe the conservation of energy in a chemical reaction?

• Energy is neither created nor destroyed during a chemical reaction.

• The energy contained in the bonds of reactant molecules always equals the energy contained in the bonds of product molecules.

• If the energy of a system increases, then the energy of the surroundings decreases by the exact same amount.

• Energy can only be transferred from one form to another.

Why do chemical reactions usually involve a change in energy?

• The process of formation of bonds or breaking bonds during a chemical reaction releases and absorbs energy respectively.

• The process of splitting the nucleus of an atom releases large amounts of energy.

• In chemical reactions, atoms are destroyed and converted into energy.

• The nuclei move faster during chemical reactions and so require more energy.

Based on this chemical equation, which of the following statements is true?

• 117 kJ of energy is released when a single molecule of MgCO3 decomposes.

• 117 kJ of energy is needed to make 1 mole of MgCO3 decompose.

• 117 kJ of energy is needed to make 42 g of MgCO3 decompose.

• 117 kJ of energy is needed to make a single molecule of MgCO3 decompose.

• 117 kJ of energy is released when 1 mole of MgCO3 decomposes.

All of the following vary in a closed system except ...........

• energy

• mass

• temperature

• enthalpy

Which of the following statements is correct?

• In the isolated system, exchange of heat occurs with the surrounding.

• In the isolated system, exchange of heat and substance occurs with the surrounding.

• In the isolated system, exchange of heat or substance does not occur with the surrounding.

• In the isolated system, exchange of the substance occurs with the surrounding.

Which of the following is the best description for the temperature of an object?

• The measurement of the average kinetic energy of the matter's molecules, which indicates the hotness and coldness of that object

• The measurement of the average potential energy of the matter's molecules, which indicates the hotness and coldness of that object

• The measurement of the average speed of the matter's molecules, which indicates the hotness and coldness of that object

• The measurement of the average kinetic energy of the surrounding particles around the matter's molecules, which indicates the hotness and coldness of that object

study the following graph ,if the reaction is exothermic or endothermic ?

• exothermic

• endothermic

148 calories equal ……. Joules approximately

• 6.61

• 35.4

• 148

• 619