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ycow [4]
3 years ago
13

A coffee-cup calorimeter initially contains 125 g water at 24.28C. Potassium bromide (10.5 g), also at 24.28C, is added to the w

ater, and after the KBr dissolves, the final temperature is 21.18C. Calculate the enthalpy change for dissolving the salt in J/g and kJ/mol. Assume that the specific heat capacity of the solution is 4.18 J/8C
Chemistry
1 answer:
iren2701 [21]3 years ago
6 0

Answer:

The solution is given below

Explanation:

Heat, q= mc∆T

q= 125g x 4.18 J/g∙°C x (21.18x- 24.28) °C

q=  -1619.75J

NEGATIVE SIGN INDICATES THAT HEAT IS ABSORBED.

Enthalpy Change, ∆H = 1619.75 7/ 10.5 g

                                     = 154.26 J/g

No. of moles of KBr = Mass of KBr/ Molecular Weight of KBr

                                =10.5g/119gmol-1

                                =0.088 mol

∆H= 1619.75 J/ 0.088 mol

      = 18.41 kJ/mol  

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The molarity of the solution: 0,27M

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A student collected a 47.5 mL sample of gas in the lab at 0.8 atm pressure and 29.00C. What volume would this gas sample occupy
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3 years ago
How you could use the scientific method to learn whether water really does take longer to boil if you are watching it.​
Alenkasestr [34]

Answer:

Please find the detailed explanation below

Explanation:

A scientific method is a sequence of steps that is used to solve a problem. Every scientific method begins with a problem that needs to be solved.

Hence, in order to determine whether water really does take longer to boil if you are watching it, we employ the steps involved in a scientific method.

1) Ask a question/Make observation: This must initiate the process. The observation/question made here is that DOES WATER TAKE LONGER TIME TO BOIL WHEN WATCHED?

2. Formulating hypothesis; an hypothesis is a testable prediction of a possible solution to the stated problem. In this case, an hypothesis could read: IF water is watched while boiling, THEN it will take a longer time to boil. A hypothesis must be tested for it to be proved or disproved.

3. Test hypothesis: The formulated hypothesis is tested via conducting an experiment. The set up of the experiment can involve one group where water is boiled while watching it and another where water is boiled without watching. The former group is called Experimental group, while the latter group is called Control group. The time it takes for each group of water to boil will be recorded.

The independent variable (manipulated variable) will be the WATCHING, while the dependent variable (tested/responding variable) will be the TIME IT TAKES FOR WATER TO BOIL

4. Analyse the data; the data refers to the recorded time for each group of water. This will be analysed and compared.

5. Make conclusion; the conclusion depends on the result, which is the recorded time for each group of boiled water. Based on the result, the hypothesis can either be rejected or accepted. For example, if the control group boils faster than the experimental group, our hypothesis will be accepted but if otherwise, the hypothesis will be rejected.

Therefore, via the scientific method, it can be determined if it really takes longer time for water to boil while watched.

8 0
4 years ago
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