Chemistry, 18.09.2019 04:10 lmoleary7466

Asample of ammonium nitrate, weighing 25.2 g, was added to a 150.0 ml container of h2o at 20.0 °c, and then is thoroughly dissolved. the final temperature of the mixture is 8.5 °c. find how much heat (kj) was lost/gained by the solution (surroundings).

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Answer from: wytchnia

Explanation:

It is known that the relation between heat energy, specific heat and change in temperature is as follows.

q = $m \times C \times \Delta T$

where, q = heat released or absorbed

m = mass of substance

C = specific heat

$\Delta T$ = change in temperature

It is given that mass is 25.2 g and it is added to 150 ml container so total mass will be (25.2 g + 150 g) = 175.2 g, $T_{1}$ is $20^{o}C$ , $T_{2}$ is $8.5^{o}C$ , and specific heat of water is 4.184 $J/g ^{o}C$ .

Hence, putting the given values into the above formula as follows.

q = $m \times C \times \Delta T$

= $175.2 g \times 4.184 J/g^{o}C \times (8.5 - 20)^{o}C$

= $175.2 g \times 4.184 J/g^{o}C \times -11.5^{o}C$

= -8430 J

As, 1 J = 0.001 kJ. Hence, -8430 J will also be equal to -8.43 kJ. The negative sign indicates that heat is being lost.

Thus, we can conclude that heat (kJ) was lost by the solution (surroundings) is 8.43 kJ.

Answer from: Quest

it means there are 3 atoms of oxygen

Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.

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Asample of ammonium nitrate, weighing 25.2 g, was added to a 150.0 ml container of h2o at 20.0 °c, a...