What causes a liquid to change into vapor

Identify the variables in the investigation: An investigation was done with an electromagnetic system made from a battery and wi

kondaur [170]

Answer:

Independent: sizes of nails

Dependent: number of paper clips

Controlled: Battery, wire and type of nails

Explanation:

An independent variable is a variable which when changes does not the effect the results of the experiment. It does not depends upon the dependent variable.

A dependent variable is defined as a variable which is affected when the independent variable is changed by the researcher or the experimenter. It depends greatly upon the independent variable.

While a controlled variable is that variable whose value is not changed in an experiment. It contains all the constants.

In the context,

the independent variable are : sizes of nails

the dependent variables are : number of paper clips

the Controlled variables are: Battery, wire and type of nails

8 0

2 years ago

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

2 years ago

Balance the following redox equation in acidic solution using the smallest integers possible and select the correct coefficient

romanna [79]

Answer:

Coefficient of $H^{+}(aq)$ is more than 4

Explanation:

Oxidation: $Sn^{2+}(aq)\rightarrow Sn^{4+}(aq)$

Balance charge: $Sn^{2+}(aq)-2e^{-}\rightarrow Sn^{4+}(aq)$ ......(1)

Reduction: $Cr_{2}O_{7}^{2-}(aq)\rightarrow Cr^{3+}(aq)$

Balance Cr: $Cr_{2}O_{7}^{2-}(aq)\rightarrow 2Cr^{3+}(aq)$
Balance O and H in acidic medium: $Cr_{2}O_{7}^{2-}(aq)+14H^{+}(aq)\rightarrow 2Cr^{3+}(aq)+7H_{2}O(l)$
Balance charge: $Cr_{2}O_{7}^{2-}(aq)+14H^{+}(aq)+6e^{-}\rightarrow 2Cr^{3+}(aq)+7H_{2}O(l)$ .......(2)