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3 years ago

How many neutrons does element X have if its atomic number is 45 and its mass number is 156?

1 answer:

3 0

Each atom has three atomic particles, which are electron, neutron and proton. The number of proton an atom has determines its atomic number. For an atom to be neutral, the number of proton and electron must be equal.
Mass number is defined as the summation of proton and neutron in an atom.
For the question given above, the number of proton is 45, because the atomic number is 45 and the number of electron too is 45.
To find the number of neutron; Mass number = proton + neutron
Neutron number = Mass number - proton number
Neutron number = 156 - 45 = 111.
Therefore the number of neutron in element X is 111.

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3 years ago

In reverse osmosis, water flows out of a salt solution until the osmotic pressure of the solution equals the applied pressure. I

Vsevolod [243]

Answer : The final concentration of the seawater is, 2.909 mole/L

Explanation :

Formula used for osmotic pressure :

$\pi=CRT$

where,

$\pi$ = osmotic pressure = 70.0 bar = 70 atm

R = solution constant = 0.0821 Latm/moleK

T= temperature of solution = $20^oC=273+20=293K$

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Now put all the given values in the above formula, we get the concentration of seawater.

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4 years ago

¿Qué establece la ley de la conservación de la materia? Explicar.

masya89 [10]

La materia no se crea ni se destruye solo se transforma

Explanation:

«En toda reacción química la masa se conserva, es decir, la masa total de los reactivos es igual a la masa total de los productos».

Los átomos ni de crean ni se destruyen,durante una reacción química.Por lo tanto una ecuación química ha de tener el mismo numero de atomos de cada elemento a ambos lados de la flecha. Se dice entonces que la ecuación esta balanceada

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3 years ago

Determine whether or not the mixing of each pair of solutions results in a buffer. Show all work!

tia_tia [17]

Answer:

a) Acidic buffer

b) No buffer

c) Acidic buffer

d) Basic buffer

e) Basic buffer

Explanation:

a) 75.0 mL of 0.10 M HF ; 55.0 mL of 0.15 M NaF -Acidic buffer

Mixing of 75.0 mL of 0.10 HF and 55.0 mL of 0.15 mL NaF results in acidic buffer. HF/NaF is a buffer of weak acid and its conjugate base. F- is the conjugate base of acid,HF.

b.) 150.0 mL of 0.10 M HF ; 135.0 mL of 0.175 M HCl-No buffer

Mixing HF and HCl will not results in a buffer. Both are acids, and no conjugate base is present.

c.) 165.0 mL of 0.10 M HF ; 135.0 mL of 0.050 M KOH-Acidic buffer

HF reacts with KOH to form KF. F- is a conjujate base of HF. As volume and concentration of HF is more than KOH, therefore, HF will remain after reaction with KOH. HF/KF will be a buffer of weak acid and its conjugate base.

d.) 125.0 mL of 0.15 M CH3NH2 ; 120.0 mL of 0.25 M CH3NH3Cl -Basic buffer

CH3NH2/CH3NH3+ is a buffer of weak base and its conjugate acid.

e.) 105.0 mL of 0.15 M CH3NH2 ; 95.0 mL of 0.10 M HCl-Basic buffer

CH3NH2 is a weak base and HCl is a strong acid. CH3NH2 reacts with HCl to form its conjugate acid CH3NH3+. Volume and concentration of CH3NH2 is more as compared to HCl and hence, will remain in the soution after reactionf with HCl.

CH3NH3+/CH3NH2 is a buffer of weak base and its conjugate acid.

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4 years ago