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Maslowich
3 years ago
8

A chemistry instructor provides each student with 8 test tubes at the beginning of the year. If there are 28 students per class,

how many test tubes are required for three chemistry classes?
Chemistry
1 answer:
Ann [662]3 years ago
7 0
Answer :8*28=224
224*3=672
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Substance A has the following properties.
givi [52]

A curve of temperature vs. time for the entire heating process.

The sample is heated up to 100.°C, therefore, the heat and time required to heat the sample to its boiling point, the heat and time required to boil the sample, and the heat and time required to heat the sample from its boiling point to 100.°C are needs to be calculated.

i ) Calculating the heat and time required to heat the sample to its boiling point:

Boiling point = 85°C

C(liquid) = 2.5 J/g °C

The heat required up to melting the sample is calculated in the previous parts. Therefore, the heat required to heat the sample from -20°C to 85°C can be calculated as,

Therefore, T f = 85°C  and T i = - 20°C

Plug in the values in the specific heat formula to calculate the heat energy required to heat the sample to its melting point,

q3 = 25 g ×  2.5 J/g °C × [85 - (-20)]°C

     = 25 J/°C ×[85+20]°C

     = 6562.5 J

The total heat energy required for heating the sample from initial temperature to boiling point is:-

q1 + q2 + q3 = 500 J + 4500 J + 6562.5 J

                    = 11562.5 J

The Rate of heating = 450 J/min

450. J = 1 min

   11562.5 J = ? min

11562.5 J × 1min/450 J = 25.69 min

ii) Calculating the heat and time required to boil the sample:

∆H Vap = 500 J/g

The boiling is the phase change from liquid to gas at 85°C, therefore, the heat required to boil the sample can be determined

q4= m × ∆Hvap

    = 25 g × 500 J/g

   = 12500 J

Thus, total heat required to this phase change is q1 + q2 + q3 + q4  = 500 J + 4500 J +6562.5  J + 12500 J = 24062.5 J

The Rate of heating = 450 J / min

450 J = 1 min

24062.5 J = ? min

24062.5J ×  1min / 450 J = 53.47 min

iii) Calculating the heat and time required to heat the sample from its boiling point to 100°C

C gas = 0.5 J / g °C

The heat required to boil the sample is calculated in the previous parts. Therefore, the heat required to heat the sample from 85°C to 100°C can be calculated as,

Therefore, T f = 100.°C  and T i = 85°C

q5 = 25 g ×  0.5 J / g °C × [100 - 85] °C

    = 25 J / °C ×15 °C

    = 187.5  J

The total heat energy required for heating the sample from initial temperature to 100°C is

q1 + q2 + q3 + q4 + q5 = 500 J + 4500 J + 2625J + 12500 J + 187.5 J

                                      =24250 J

The Rate of heating = 450 J / min

  450. J = 1 min

 24250 J=? min

Thus, heating the sample to 100.°C takes a total of 53.89 min.

iv) Draw a curve of temperature vs. time for the entire heating process:-

Temperature °C     Temperature K     Heat energy (J)     Time (min)

 -40 °C                       233                             0                     0

-20 °C                          253                          500                  1.11    

Melting -20 °C             253                        5000                   11.11

85 °C                         358                         11562.5              25.69

Boiling 85 °C             358                           24062.5          53.475              

100  °C                       373                             24250          53.89

Hence, the graph for the result is in the image.

Learn more about temperature here:-brainly.com/question/24746268

#SPJ4

4 0
2 years ago
What is the percent composition by mass of each element in Co(HSO4)2?
MrRissso [65]

Answer:

54.1 % Ca, 43.2 % O, 2.7% H

Explanation:

Molecular formula for calcium hydroxide is Ca(OH)₂

As we don't have a mass of Ca(OH)₂ to find out the percentage composition, we consider that the question refers to 1 mol of compound.

1 mol of hydroxide weighs 74.08 g

1 mol of hydroxide has 1 mol of Ca, therefore 40.08 g are Ca

2 moles of O therefore 32g are O

2 moles of H therefore 2 g are H

Percentage composition is known as (Mass of element/Total mass) . 100

(40.08 / 74.08) . 100 = 54.1 %

(32 / 74.08) . 100 = 43.2 %

(2 / 74.08) . 100 = 2.7%

im a smart one

7 0
2 years ago
How do you analyze chemical evidence?
Sever21 [200]
BIOLOGICAL & CHEMICAL EVIDENCE ANALYSIS
There are many different types of evidence that can be found at a crime scene. Physical evidence can be collected at the crime scene such as a murder weapon. Chemical evidence is any residue from liquids that such as poison and drugs. Biological evidence is when hair or skin from a persons body has been transferred to a physical surface and then be collected and tested.

This evidence can be used to find out what exactly happened at the scene of the crime, the history behind the crime and who was involved and could have committed it.

Our experts test and analyse many forms of evidence, which is vital when finding out the various incidences that happened at a crime scene.
3 0
3 years ago
What is 5.0553 x 10^-4 in standard notation?
Talja [164]

Answer:

0.00050553

Explanation:

when the power of ten is negative, move the decimal to the left

hope this helped!

6 0
3 years ago
A material has a density of 8.9 g/cm^3. You have 3 grams of the substance. How much space does it take up? a. 0.3cm3 b. 3.0 cm3
My name is Ann [436]
D = m/ V

8.9 = 3 / V

V = 3 / 8.9

V = 0.3 cm³

Answer A

hope this helps!
6 0
3 years ago
Read 2 more answers
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