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Ivanshal [37]
3 years ago
14

A student wants to carry out flame tests on these three chemicals. Describe how to carry out a flame test.

Chemistry
1 answer:
neonofarm [45]3 years ago
3 0

Answer:

Flame test is one of the chemical tests that can be used to identify a metal or metaloid

in an ionic compound.

Explanation:

Flame test is guided by a principle that when an unknown metal is heated, heat of the flame converts the metal ions into atoms which become excited and emit visible light.

To carry out flame test in a laboratory the following instruments are required:

--> a wire loop

--> Bunsen burner

--> the chemical compound under observation

--> protective wears.

The procedure involves the following steps:

--> turn on the Bunsen burner and adjust the barrel of the burner roll the flame is blue.

--> using a clean wire loop deep into a beaker containing hydrochloric acid.

--> to ensure that the loop is clean, it will give the same blue colour of the flame when heated.

--> deep the loop in the acid again and then use it to pick few grains of the metal.

--> place the wire loop in the side of the flame and observe the colour of the flame.

Result of flame tests of some metallic ion will show the following:

--> sodium ion will give yellow colour flame

--> potassium ion will give lilac colour flame

--> calcium ion will give orange-red colour flame

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How much energy must be removed from a 94.4 g sample of benzene (molar mass= 78.11 g/mol) at 322.0 K to solidify the sample and
Kay [80]

Answer : The energy removed must be, 29.4 kJ

Explanation :

The process involved in this problem are :

(1):C_6H_6(l)(322K)\rightarrow C_6H_6(l)(279K)\\\\(2):C_6H_6(l)(279K)\rightarrow C_6H_6(s)(279K)\\\\(3):C_6H_6(s)(279K)\rightarrow C_6H_6(s)(205K)

The expression used will be:  

Q=[m\times c_{p,l}\times (T_{final}-T_{initial})]+[m\times \Delta H_{fusion}]+[m\times c_{p,s}\times (T_{final}-T_{initial})]

where,

Q = heat released for the reaction = ?

m = mass of benzene = 94.4 g

c_{p,s} = specific heat of solid benzene = 1.51J/g^oC=1.51J/g.K

c_{p,l} = specific heat of liquid benzene = 1.73J/g^oC=1.73J/g.K

\Delta H_{fusion} = enthalpy change for fusion = -9.8kJ/mol=-\frac{9.8\times 1000J/mol}{78g/mol}=-125.6J/g

Now put all the given values in the above expression, we get:

Q=[94.4g\times 1.73J/g.K\times (279-322)K]+[94.4g\times -125.6J/g]+[94.4g\times 1.51J/g.K\times (205-279)K]

Q=-29427.312J=-29.4kJ

Negative sign indicates that the heat is removed from the system.

Therefore, the energy removed must be, 29.4 kJ

3 0
3 years ago
The heat of vaporization of 1-pentanol is 55.5 kJ/mol, and its entropy of vaporization is 148 J/K.mol. What is the approximate b
____ [38]

Answer:

Approximately 100 °C.

Explanation:

Hello,

In this case, since the entropy of vaporization is computed in terms of the heat of vaporization and the temperature as:

\Delta S_{vap}=\frac{\Delta H_{vap}}{T}

We can solve for the temperature as follows:

T=\frac{\Delta H_{vap}}{\Delta S_{vap}}

Thus, with the proper units, we obtain:

T=\frac{55500J/mol}{148J/(mol*K)} =375K\\\\T=102 \°C

Hence, answer is approximately 100 °C.

Best regards.

6 0
3 years ago
Most bones are connected at Joints by​
Anuta_ua [19.1K]

Answer:

Los huesos se mantienen unidos a otros huesos a través de unas largas tiras fibrosas llamadas ligamentos. El cartílago, una sustancia flexible y elástica que contienen las articulaciones, sujeta los huesos y los protege en los puntos donde varios huesos friccionan entre sí.

7 0
3 years ago
Observando la siguiente reacción química: 3Fe + 4H2 O Fe3 O4 + H2(g) 4. Contesta ¿Por qué si se lleva a cabo en el recipiente ab
wolverine [178]

Answer:

La reacción se convierte en reversible porque en un recipiente cerrado el gas no escapa y puede reaccionar con el óxido

Explanation:

Basados en la reacción:

3Fe + 4H₂O → Fe₃O₄ + 4H₂(g)

<em>3 moles de hierro con 4 moles de agua producen 1 mol de óxido de hierro y 4 moles de hidrógeno (gas)</em>

Cuando la reacción se está produciendo con un recipiente abierto, todo el gas de hidrógeno está escapando a la atmósfera y no habrá forma de que reaccione con el óxido de hierro.

Pero, si el recipiente está cerrado, el hidrógeno no podrá escapar y podrá reaccionar con el óxido de hierro, así:

Fe₃O₄ + 4H₂(g) → 3Fe + 4H₂O

De esta manera,

<h3>la reacción se convierte en reversible porque en un recipiente cerrado el gas no escapa y puede reaccionar con el óxido</h3>
5 0
3 years ago
A 25 mL sample of 0.100 M HNO3 completely reacts with NaOH according to this equation:
Anastasy [175]
It is a good thing that you already have answered the first question. Now, moving on to the second question, there exist an equation for the neutralization of acid by a base that is shown below,
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Now, all the variables in the equation are given except for our unknown which is the V₂. Substituting the known values from the given above,
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The value of V₂ from the equation above is 50 mL. Therefore, 50 mL of 0.05 M NaOH solution will be needed to completely react with HNO3. 
6 0
3 years ago
Read 2 more answers
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