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3 years ago

5

The ____ formula is the combination of chemical symbols and numbers that represent the elements and number of atoms within a com

pound.

1 answer:

Strike441 [17]3 years ago

8 0

Answer:

Chemical

Explanation:

The Chemical formula is the combination of chemical symbols and numbers that represent the elements and number of atoms within a compound.

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Is water a good solvent choice for recrystallization of NaCl?

nika2105 [10]

Answer:

Water is not a good solvent choice.

Explanation:

While water is good solvent because of its polotiry. Water is not good for the recrystallization process becuase being a good recystallization solvent means that a compound must dissolves easily when the solvent is warm, but that is less soluble at room temperature or when cooled in an ice bath. Water has the dissolves when warm part down. But for the cooled part which is the most important it can not do.

7 0

3 years ago

What is the acceleration object velocity of +25m/s to rest in 5.0 s

Irina-Kira [14]

The average acceleration is -5.0 m·s⁻².

The formula for acceleration (<em>a</em>) is

$a = \frac{v_{f}- v_{i}}{t}$

$v_{f}$ = 25 m·s⁻¹; $v_{i}$ = 0; $t$ = 5.0 s

∴ $a = \frac{0-25}{5.0}$ = -5.0 m·s⁻²

The negative sign tells you that the object is <em>slowing down</em>, i.e., it is <em>decelerating</em>.

4 0

3 years ago

If a buffer solution is 0.220 M in a weak acid ( Ka=7.4×10−5) and 0.540 M in its conjugate base, what is the pH?

valkas [14]

Answer: the pH of the solution is 4.52

Explanation:

Consider the weak acid as Ha, it is dissociated as expressed below

HA H⁺ + A⁻

the Henderson -Haselbach equation can be expressed as;

pH = pKa + log( [A⁻] / [HA])

the weak acid is dissociated into H⁺ and A⁻ ions in the solution.

now the conjugate base of the weak acid HA is

HA(aq) {weak acid} H⁺(aq) + A⁻(aq) {conjugate base}

so now we calculate the value of Kₐ as well as pH value by substituting the values of the concentrations into the equation;

pKₐ = -logKₐ

pKₐ = -log ( 7.4×10⁻⁵ )

pKₐ = 4.13

now thw pH is

pH = pKₐ + log( [A⁻] / [HA])

pH = 4.13 + log( [0.540] / [0.220])

pH = 4.13 + 0.3899

pH = 4.5199 = 4.52

Therefore the pH of the solution is 4.52

6 0

3 years ago

A thermometer is placed in a beaker full of water that has been sitting on the lab table for a few hours. The beaker is placed o

krek1111 [17]

Based on the information I would assume B, 73 degrees...

It shouldn't be A, 4 minutes on the burner should increase the temperature.

If it were D, it would be beyond boiling, and water takes a decent amount of energy to heat, D should be all vapor.

Same logic for C, it's basically almost boiling.

I would say 73 degrees seems most reasonable for 4 minutes.

7 0

3 years ago

Read 2 more answers

The activation energy for a reaction is changed from 184 kJ/mol to 59.0 kJ/mol at 600. K by the introduction of a catalyst. If t

11111nata11111 [884]

Answer:

The catalyzed reaction will take 2.85 seconds to occur.

Explanation:

The activation energy of a reaction is given by:

$k = Ae^{-\frac{E_{a}}{RT}}$

For the reaction without catalyst we have:

$k_{1} = Ae^{-\frac{E_{a_{1}}}{RT}}$ (1)

And for the reaction with the catalyst:

$k_{2} = Ae^{-\frac{E_{a_{2}}}{RT}}$ (2)

Assuming that frequency factor (A) and the temperature (T) are constant, by dividing equation (1) with equation (2) we have:

$\frac{k_{1}}{k_{2}} = \frac{Ae^{-\frac{E_{a_{1}}}{RT}}}{Ae^{-\frac{E_{a_{2}}}{RT}}}$

$\frac{k_{1}}{k_{2}} = e^{\frac{E_{a_{2}} - E_{a_{1}}}{RT}$

$\frac{k_{1}}{k_{2}} = e^{\frac{59.0 \cdot 10^{3}J/mol - 184 \cdot 10^{3} J/mol}{8.314 J/Kmol*600 K} = 1.31 \cdot 10^{-11}$

Since the reaction rate is related to the time as follow:

$k = \frac{\Delta [R]}{t}$

And assuming that the initial concentrations ([R]) are the same, we have:

$\frac{k_{1}}{k_{2}} = \frac{\Delta [R]/t_{1}}{\Delta [R]/t_{2}}$

$\frac{k_{1}}{k_{2}} = \frac{t_{2}}{t_{1}}$

$t_{2} = t_{1}\frac{k_{1}}{k_{2}} = 6900 y*1.31 \cdot 10^{-11} = 9.04 \cdot 10^{-8} y*\frac{365 d}{1 y}*\frac{24 h}{1 d}*\frac{3600 s}{1 h} = 2.85 s$

Therefore, the catalyzed reaction will take 2.85 seconds to occur.

I hope it helps you!

4 0

3 years ago