Two aqueous solutions are both at room temperature and are then mixed in a coffe

Question

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statement is TRUE? The products and reactants have a same potential energy. Energy is leaving the system during reaction. The reaction is exothermic. This type of experiment will provide data to calculate Delta E_rxn. The products have higher potential energy than the reactants. Place the following in order of increasing radius. Br Na Rb Rb

Explanation / Answer

27 ) when two aqueous solutions mixed at same temp. , then the temp. of the system (reaction mixture) is decreases) , this means that reaction is endothermic (heat is absorbed in the system), this means that product has higher energy than reactant. so, only option 'E' is correct (true) statement.

28) Increasing order of radius of bromine, sodium and rubidium are as,

Br<Na<Ru ,

Br= 1.19 A, Na= 1.54 A, Ru= 2.26 A,,

so the option 'B' is correct.

29) as the frequency of photon increases,

the wavelength decreases,

frequency and energy are directly proportional , means as the energy increases frequency increases.

the wavelength and frequency are inversally proportional that is as the frequency of photon increases wavelength decresaes, ,

there fore the option D is correct,

30 ) from the spectrum of electronic transitions of hydrogen atom,

the n=2 to n=4 transitions has higher energy, this means that it has shortest wavelength.

as energy increases wavelength decreases.

so the option E is correct.

31) Zn has the atomic no. 30, it has 30 electrons,

so the core electrons are 28 , 2 electrons in the outer shell,

so the option C is correct.

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