Chemistry, 28.03.2021 06:10 kyrabrown33

se disuelve dicromato de potasio k2Cr2O7 en agua para hacer 300mL de solucion. si la molaridad de la solucion se desea que sea 0.125 M; ¿cuantos moles de soluto se necesitan y cuantos gramos habrá que pasar?

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Answer from: madeleine1102

0.0375 moles.

11.03 gramos.

Explanation:

¡Hola!

En este caso, dado que la definición de molaridad viene dada por:

$M=\frac{mol}{V}$

En dónde el volumen viene dado en litros, primero es necesario convertir 300 mL a litros:

$V=300mL*\frac{1L}{1000mL}=0.300L$

Ahora, cómo se nos da la molaridad y el volumen, es posible calcular las moles como sigue:

$mol=M*V\\\\mol=0.125mol/L*0.300L\\\\mol=0.0375mol$

Seguidamente, como la masa molar del dicromato de potasio es 294.18 g/mol, la masa a pesar será de:

$m=0.0375mol*\frac{294.18g}{1mol} \\\\m=11.03g$

¡Saludos!

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.

Answer from: Quest

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃ → 3 nicl₂ + 2 albarium and copper bromideba + cubr → no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn → znso₄ + na

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