A chemist prepares a solution of sodium chloride(NaCl) by measuring out 25.4g of sodium chloride into a 100ml volumetric flask a
nd filling the flask to the mark with water. Calculate the concentration in mol/L of the chemist's sodium chloride solution. Round your answer to significant digits.
2 answers:
Answer: 4 molL-1
Explanation:
Detailed solution is shown in the image attached. The number of moles of NaCl is first obtained. Since the molarity must be in units of molL-1, the volume is divided by 1000 and the formula stated in the solution is applied and the answer is given to one significant figure.
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Explanation:
Upon dissolution of KCl heat is generated and temperature of the solution raises.
Therefore, heat generated by dissolving 0.25 moles of KCl will be as follows.
= 4.31 kJ
or, = 4310 J (as 1 kJ = 1000 J)
Mass of solution will be the sum of mass of water and mass of KCl.
Mass of Solution = mass of water + (no. of moles of KCl × molar mass)
= 200 g +
= 200 g + 13.625 g
= 213.625 g
Relation between heat, mass and change in temperature is as follows.
Q =
where, C = specific heat of water =
Therefore, putting the given values into the above formula as follows.
Q =
4310 J =
Thus, we can conclude that rise in temperature will be .
Answer:
Heating this gas to 55 °C will raise its volume to 6.87 liters.
Assumption: this gas is ideal.
Explanation:
By Charles's Law, under constant pressure the volume of an ideal gas is proportional to its absolute temperature
(the one in degrees Kelvins.)
Alternatively, consider the ideal gas law:
.
is the number of moles of particles in this gas.
is the ideal gas constant.
is the pressure on the gas. The question states that the pressure on this gas is constant.
Therefore the volume of the gas is proportional to its absolute temperature.
Either way,
.
.
For the gas in this question:
- Initial volume:
.
Convert the two temperatures to degrees Kelvins:
- Initial temperature:
.
- Final temperature:
.
Apply Charles's Law:
.