Chemistry, 23.07.2020 21:01 winwinphyo

Honors Calormetry Activity In this activity, you will plan and conduct an investigation on energy transfers between two liquids of different temperatures.

Objective: Plan and then conduct an investigation on energy transfer between two liquids of different temperatures.
Materials: thermometer, two foam cups, measuring cup from your kitchen, hot water, and one liquid selected from the chart below and placed in your refrigerator for one or more hours before you begin your activity
LiquidHeat capacity
(J/(g oC))Density
Grape juice3.61.06 g/mL
Whole milk3.771.04 g/mL
Orange juice3.731.05 g/mL
Tomato juice 3.981.03 g/mL

Caution: You will be working with hot water in this lab. Be very careful as you pour so you do not burn yourself. Also, be sure to read your thermometer carefully. The numbers on the thermometer scale refer to the line under the number. Lastly, it's important to perform certain steps quickly and efficiently to minimize heat loss to the surroundings.

Procedure:
1.Read the entire procedure before you begin the experiment.
2.Use the metric scale on your measuring cup to measure 237 mL (1 cup) of your selected refrigerated liquid. Pour this liquid into one of the foam cups.
3.Now, get the hottest water possible from the faucet on your sink. Use the metric scale on your measuring cup to measure 237 mL (1 cup) of hot water. Pour this water into the other foam cup.
4.Quickly measure the temperature of the cold liquid and the hot water. Record the temperatures in a data table.
5.Very quickly pour the hot water into the cold liquid. Place the thermometer in the mixture. Invert the cup that contained the cold liquid over the cup containing the water mixture.
6.Keeping the bulb of the thermometer in the liquid, check the temperature reading about every 20 seconds until the temperature stabilizes. Keep the lid (inverted cup) in place as much as possible. When the temperature is constant (this will happen very quickly), record this temperature in a data table as the final Hltemperature.

Data:
Create a data table of for your measurements and calculations. Two measurements are provided for you. Record the other measurements needed for this activity.
Volume of cold liquid237 mL (1 cup)
Volume of hot water237 mL (1 cup)

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Answer from: Quest

the answer is definitely c.

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they vary. it used to be meat, grain, bread, candy, beverages, donuts, and fruits/vegetables. now they added exercise in.

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Zinc contains about 30 protons

Answer from: Quest

the missing options are :

(1) lower boiling point and a lower freezing point(2) lower boiling point and a higher freezing point(3) higher boiling point and a lower freezing point(4) higher boiling point and a higher freezing point

answer : the correct answer is option (3) higher boiling point and a lower freezing point

explanation :

when a non volatile solute is added to a solvent like water, it results in elevation of boiling point.

let us find the increase in boiling point of water when cacl₂ is added to water to make a solution of 1 m

step 1 : find molality of the solution

let us assume we have 1 l of solution.

$m = \frac{moles (solute)}{l ( solution)}$

$1 m = \frac{moles (cacl_{2})}{1 l }= 1 mol cacl_{2}$

let us convert this to grams of cacl₂.

molar mass of cacl2 is 111 g/mol

grams of cacl₂ = $1 mol \times \frac{111g}{mol} = 111 g cacl_{2}$

mass of solute = 111 g

assuming density of solution same as water which is 1g/ml we have ,

mass of solution = density * volume

mass of solution = $\frac{1g}{ml} \times 1000 ml = 1000 g$

mass of solution = mass of solvent + mass of solute

mass of solute = 1000g - 111g

mass of solute 889 g = 0.889 kg

the molality of the solution can be calculated as

$molality = \frac{mol (solute)}{kg ( solvent)}$

$molality = \frac{1mol}{0.889kg}$

molality = 1.12 m

step 2 : find boiling point elevation.

the elevation in boiling point is calculated as

$\bigtriangleup t_{b} = i \times k_{b} \times m$

here δtb = boiling point elevation

i = vant hoff factor which is the number of ions formed by the solute .

cacl₂ dissociates as $cacl_{2} \rightarrow ca^{2+} + 2 cl^{-}$

it forms 3 ions . therefore,

i = 3

m = molality which is 1.12 m

kb is constant for a given solvent. for water it is 0.512

$\bigtriangleup t_{b} = 3 \times 0.512 \times 1.12$

$\bigtriangleup t_{b} = 1.7$

the boiling point of water increases by 1.7 °c

step 3: find freezing point depression.

when a non volatile solute is added to water, it results in decrease in freezing point.

the formula to find freezing point depression is

$\bigtriangleup t_{f} = i \times k_{f} \times m$

kf is constant for water and its value is 1.86

$\bigtriangleup t_{f} = 3 \times 1.86 \times 1.12$

$\bigtriangleup t_{f} = 6.2$

the freezing point of water decreases by 6.2 °c

therefore we can say that, the solution will have a higher boiling point and a lower freezing point

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Honors Calormetry Activity In this activity, you will plan and conduct an investigation on energy t...

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