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Kisachek [45]
3 years ago
6

Why are chemists interested in studying thermochemistry? a. Heat is often absorbed during reactions.b. Heat is often released du

ring a chemical reaction, but never absorbed. c. Heat is often released during chemical reactions.d. Heat is often absorbed in a chemical reaction, but never released.
Chemistry
1 answer:
Wittaler [7]3 years ago
6 0

Answer:

a. Heat is often absorbed during reactions.

c. Heat is often released during chemical reactions.

Explanation:

Thermochemistry -

The study of thermochemistry involve the change in the amount of heat , during any physical or chemical process , is referred to as thermodynamics .

The focus of thermochemistry is on the changing amount of energy in the form of heat , on the system with respect to the surroundings .

The process like boiling , melting , sublimation , may require energy or releases energy , and hence are studied under thermochemistry .

Hence , from the given question ,

The correct options are -  a , c.

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Student conducts an experiment to determine the enthalpy of solution for lithium chloride dissolved in water. the student combin
nirvana33 [79]

Answer:-  \Delta H_s_o_l_n=-37.2\frac{kJ}{mol}

Solution:- First of all we calculate the heat absorbed or released when the solute is added to the solvent. Here the solute is LiCl and the solvent is water.

To calculate the heat absorbed or released we use the formula:

q=ms\Delta T

q = heat absorbed or released

m = mass of solution

s = specific heat capacity

and \Delta T = change in temperature

mass of solution = mass of solute + mass of solvent

mass of solution = 5.00 g + 100.0 g = 105.0 g

(note:- density of pure water is 1 g per mL so the mass is same as its volume)

\Delta T = 33.0 - 23.0 = 10.0 degree C

s = 4.18\frac{J}{g.^0C}

Let's plug in the values in the formula and calculate q.

q = 105.0g(4.18\frac{J}{g.^0C})(10.0^0C)

q = 4389 J

To calculate the enthalpy of solution that is \Delta H_s_o_l_n we convert q to kJ and divide by the moles of solute.

moles of solute = 5.00g(\frac{1mol}{42.39g})

= 0.118 moles

q = 4389J(\frac{1kJ}{1000J}) = 4.389 kJ

\Delta H_s_o_l_n=\frac{4.389kJ}{0.118mol}

\Delta H_s_o_l_n = 37.2\frac{kJ}{mol}

Since the heat is released which is also clear from the rise in temperature of the solution, the sign of enthapy of solution will be negative.

So,  \Delta H_s_o_l_n=-37.2\frac{kJ}{mol}


4 0
2 years ago
What is the nuclear binding energy for uranium-238 in joules? Assume the following:What is the nuclear binding energy for uraniu
ruslelena [56]
Assume <span>the following: </span><span>Mass defect = 3.2008 x 10-27 kilograms</span><span>
</span><span>Use E = mc2, with c = 3 x 108 m/s
</span>
The nuclear binding energy for uranium-238 in joules is 2.8807 x 10-8 joules. 
4 0
3 years ago
Read 2 more answers
Solve the following problems on ideal gas equation. Practice makes perfect.
photoshop1234 [79]

Answer:

0.012mol

Explanation:

1.

Given parameters:

Pressure in the balloon  = 1.25atm

Volume of the balloon  = 2.5L

Unknown:

Number of moles  = ?

Solution:

We are going to used the combined gas law to solve this problem.

  PV = nRT

P is the pressure

V is the volume

n is the number of moles

R is the gas constant  = 0.082atmdm³mol⁻¹K⁻¹

 Insert the parameters and solve;

    1.25 x 2.5  = n x 0.082 x 285

       n  = 0.13mol

The number of moles is 0.13mol

2.

Given parameters:

Pressure  = 16torr;

   to atm is ;

                 760torr  = 1atm

                  16torr = \frac{16}{760}   = 0.02atm

Volume = 12L

Temperature  = 253K

Using the ideal gas law;

        PV  = nRT

       0.02x12  = n x 0.082 x 253

            n = 0.012mol

           

7 0
2 years ago
PLZ HELP what is a sign that a chemical change has happened ​
emmainna [20.7K]

Answer:

Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color change, formation of a precipitate, formation of a gas, odor change, temperature change.

4 0
2 years ago
What is the minimum mass of nh4hs that must be added to the 5.00-l flask when charged with the 0.250 g of pure h2s(g), at 25 ∘
Kay [80]
We first can get the No of moles of H2S = 0.25 x 1 mol(H2S) / 34 g (H2S)
                                                                   = 0.0074 Moles
and according to the ideal gas low:
we can get p for H2S
PV = nRT
when we have V = 5 L & n = 0.0074  & R (constant)= 0.082 & T= 25 + 273 = 298 K
By substitution:

P* (5L) = (0.0074)*(0.082)*(298)
∴ P = 0.036 atm
By assuming Kp (should be given, you just missed it) = 0.12 at 25 C°
By substitution: to get P for NH3

0.12 = X ( P + X)
0.12 = X ( 0.036 + X)
∴X^2 + 0.036 X -0.12 = 0
by solving this equation we get 
X= 0.365 atm
So to get the no of moles of NH3:
PV = nRT
0.365 * 5 = n ( 0.082*298)
∴ n = 0.075 moles 
and to get the mass on (g) =no.of moles * molar mass
                                                      0.075 * 51 = 3.825 g NH4Hs
4 0
2 years ago
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