Heat of Solution
To determine heat of solution of the given salt on water by calorimeter Principle
There are two heats of solution, the integtal heat of solution and the
differential heat of solution, The integral heat of solution is defined as the heat
absorbed or evolved when 1 nole of solute is dissolved in such a quantity of solvent
as to give a specified concentration. We could, for exanple, dissolve 1 mole of solute
in 200 moles of water. This would give a 0.5 mole % solution. The heat change would
be the integral heat of solution. Again, the mole of solute could be dissolved in 400
noles of water. This would form a 0.25 mole % solution , and the geat change would
again be the integral heat of solution. But the value may vary from that obtained when
200 noles of water are used. On the other hand, we could take such a large quantity
of 0.5 mole% solution that the addition of 1 mole of solute would make only an
insighificant change in the concentration, The heat change in this case would be the
differential heat of solution. We can present this differential heat of solution
mathematically by the expression d (....)/ dn, and we define it as the heat absorbed
when 1 mole of solute is dissolved is such a quantity of solution that no appreciable
change in the conventration take place.
Although we ma use any desired final concentration, in this experiment we
shall measure the integral heat of solution of certain salts in solutions containing 1
mole of salt in 200 moles of water and 1 mole of salt in 4000 moles of water. These
concentration are termed dilutions of 200 and 400 respectively. The integral heats of
solution of several salts are given in Table 1 . In this Table most of the values for the
heats of solution have a minus sign. This means that cooling results when solution
occurs.
Table 1 the integral heats of solution of several salts.
In calorimetric procedures it is necessary to know the heat capacity of the
calorimeter system. By heat capacity we mean the heat necessary to change the
temperature of the calorimeter system, the calorimeter proper and the solution, by
1C. This can be obtasined by introducing a measured quantity of heat by electrical
means, and then measuring the temperature rise. Heat of solution is determined by
dissolved a small known weight of the given salt in a large measured quantity (200 g)
of water in a calorimeter. The rise of fall in temperature, i.e., ...t is noted. Then ....H is
calculated by the formula
where W = water equivalent of calorimeter
m = weight of water taken
...t = change in temperature
M = molecular weight of solute
w = weight of the solute
Method
1. To determine the water equivalent of calorimeter, take a known weight of
cold water in the inner beaker of calorimeter and note its temperature. To it mix a
lnown weight of hot water of known temperature and note the temperature of
mixture
2. Remove vater from the calorimeter and dry it.
3. Now place 200 ml. of distilled water measured by means of graduated
aylinder and note the temperature.
4. Weight accurately about 5 g of the powder salt (given) and pour it quickly,
but carefully into the calorimeter. Avod splashing of the water. Immediately replace
the stopper and begin stirring for about 30 min. or so, until the mercury in the
thermometer stem is steady at least for 5 min. Read the final temperature precisely.
Use the magnifying glass for convenience in reading of the temperature. Record the
difference of the initial and final temperture, i,e, ....t
Water equivalent of calouimeter
Weight of cold water
Temperatre of cold water
Weight of hot water
Temperature of ho water
Final temperature of mixture
Heat of solution of salt:
Weight of water taken
TEmperature of water
Weight of salt added
Final temperature of solution
ความร้อนของโซลูชันการตรวจสอบความร้อนของของเกลือให้น้ำ โดยแคลอรีมิเตอร์หลัก มี heats สองของโซลูชั่น integtal ความร้อนของการแก้ปัญหาและความร้อนที่แตกต่างของโซลูชั่น ความร้อนเป็นของถูกกำหนดให้เป็นความร้อนดูดซึม หรือพัฒนาเมื่อ nole 1 ของตัวถูกละลายในนั้นปริมาณของตัวทำละลายให้ความเข้มข้นที่ระบุ เราสามารถ สำหรับ exanple ละลาย 1 โมลของตัวถูกละลายในโมล 200 ของน้ำ นี้จะให้โซลูชัน% 0.5 โมล การเปลี่ยนแปลงความร้อนจะความร้อนที่สำคัญของโซลูชันได้ อีก โมลของตัวถูกละลายไม่สามารถละลายใน 400noles น้ำ นี้จะฟอร์มโซลูชัน 0.25 โมล% , และจะเปลี่ยน geatอีก อย่างความร้อนสำคัญของโซลูชัน แต่ค่าอาจแตกต่างไปจากที่ได้รับเมื่อ noles 200 น้ำจะใช้ บนมืออื่น ๆ เราสามารถใช้ปริมาณมากของโมล 0.5% ที่เพิ่ม 1 โมลของตัวถูกละลายจะทำให้เฉพาะ ตัวinsighificant การเปลี่ยนแปลงในความเข้มข้น การเปลี่ยนแปลงความร้อนในกรณีนี้จะเป็นการความร้อนที่แตกต่างของโซลูชั่น เราสามารถนำความร้อนส่วนนี้ของโซลูชันmathematically โดย d นิพจน์ (...) / dn และเรากำหนดมันเป็นดูดซึมความร้อนเมื่อการส่วนยุบ 1 โมลของตัวถูกละลายเป็นเช่นปริมาณของโซลูชันที่ไม่เห็นเปลี่ยนแปลงใน conventration เกิดขึ้น ถึงแม้ว่าเรามาใช้มีความเข้มข้นสุดท้ายต้อง ในนี้ทดลองเราจะวัดความร้อนเป็นของโซลูชั่นของบางเกลือในโซลูชั่นที่ประกอบด้วย 1mole of salt in 200 moles of water and 1 mole of salt in 4000 moles of water. Theseconcentration are termed dilutions of 200 and 400 respectively. The integral heats of solution of several salts are given in Table 1 . In this Table most of the values for theheats of solution have a minus sign. This means that cooling results when solutionoccurs.Table 1 the integral heats of solution of several salts. In calorimetric procedures it is necessary to know the heat capacity of thecalorimeter system. By heat capacity we mean the heat necessary to change thetemperature of the calorimeter system, the calorimeter proper and the solution, by1C. This can be obtasined by introducing a measured quantity of heat by electricalmeans, and then measuring the temperature rise. Heat of solution is determined bydissolved a small known weight of the given salt in a large measured quantity (200 g)of water in a calorimeter. The rise of fall in temperature, i.e., ...t is noted. Then ....H is calculated by the formulawhere W = water equivalent of calorimeterm = weight of water taken...t = change in temperatureM = molecular weight of solutew = weight of the soluteMethod 1. To determine the water equivalent of calorimeter, take a known weight ofcold water in the inner beaker of calorimeter and note its temperature. To it mix alnown weight of hot water of known temperature and note the temperature ofmixture 2. Remove vater from the calorimeter and dry it. 3. Now place 200 ml. of distilled water measured by means of graduatedaylinder and note the temperature. 4. Weight accurately about 5 g of the powder salt (given) and pour it quickly,but carefully into the calorimeter. Avod splashing of the water. Immediately replacethe stopper and begin stirring for about 30 min. or so, until the mercury in thethermometer stem is steady at least for 5 min. Read the final temperature precisely.Use the magnifying glass for convenience in reading of the temperature. Record thedifference of the initial and final temperture, i,e, ....t Water equivalent of calouimeter Weight of cold water Temperatre of cold water Weight of hot water Temperature of ho water Final temperature of mixture Heat of solution of salt: Weight of water taken TEmperature of water Weight of salt added Final temperature of solution
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