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myrzilka [38]
3 years ago
15

A chemistry student needs 30,0 mL of pentane for an experiment. By consulting the CRC Handbook of Chemistry and Physics, the stu

dent discovers that the density of pentane is . Calculate the mass of pentane the student should weigh out. Round your answer to significant digits.
Chemistry
1 answer:
Marta_Voda [28]3 years ago
8 0

Answer:

1.878g

Explanation:

Volume = 30.0ml

Density = 0.626gcm−3

Mass = ?

Be careful in this kind of questions to check for the units. In this case one has to remember 1 mL equal 1 cm³ so density = 0.626g/ml

The relationship between all three parameters is given by the equationn below;

Mass = Density * Volume

Mass = 0.626g/ml * 30 = 1.878g

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What is the net amount of energy released when one mole of h2o(?) is produced?
german
The net amount of energy produced can be obtained from a table of enthalpy change of formation, available online.

The enthalpy change of formation indicate how much energy the 1 mole of the product (H2O) has relative to the elemental reactants (H2 and O2).  In other words, the "lost" energy equals the heat/energy released. 

For water (H2O), this value is -285.8 if the final product is a liquid under standard conditions, and -241.82 if the product is in gas form which contains some energy that could be further released.  This means that if the final product (H2O) is in liquid form, energy released is 285.8 kJ/mol.

Since water is in liquid form under standard conditions, the first value (285.8 kJ/mol) is generally appropriate.
7 0
3 years ago
What do these elements make:<br> neodymium, rhenium and sulfur
LiRa [457]

Answer:

Neodymium makes flints inside of lighters. It also takes away the green color off of glass. Rhenium is added with tungsten and molybdenum which makes filaments for lamps. Sulfur makes sulfuric acid which makes batteries and cleaners and can process ores.

Explanation:

An interesting fact for each element:

Neodymium is known for the atomic symbol Nd and the atomic number 60.

Rhenium is known for the atomic symbol Re and the atomic number 75.

Sulfur is known for the atomic symbol S and the atomic number 16.

I hope the Answer answers your question. I gave you some facts to remember those elements in the periodic table!

6 0
3 years ago
What is the relationship between the amount of carbon dioxide and the earths average temperature?
Anit [1.1K]

Answer:

carbon dioxide concentration goes down, temperature goes down. Carbon dioxide goes up temp goes up, carbon dioxide is directly related to temperature by insulating it in the earths atmosphere and if there's less of it then the temp would go down.

Explanation:

6 0
2 years ago
The enthalpy of solution (∆H) of KOH is -57.6 kJ/mol. If 3.66 g KOH is dissolved in enough water to make a 150.0 mL solution, wh
Wewaii [24]

When 3.66 g of KOH (∆Hsol = -57.6 kJ/mol) is dissolved in 150.0 mL of solution, it causes a temperature change of 5.87 °C.

The enthalpy of solution of KOH is -57.6 kJ/mol. We can calculate the heat released by the solution (Qr) of 3.66 g of KOH considering that the molar mass of KOH is 56.11 g/mol.

3.66g \times \frac{1mol}{56.11g} \times \frac{(-57.6kJ)}{mol} = -3.76 kJ

According to the law of conservation of energy, the sum of the heat released by the solution of KOH (Qr) and the heat absorbed by the solution (Qa) is zero.

Qr+Qa = 0\\\\Qa = -Qr = 3.76 kJ

150.0 mL of solution with a density of 1.02 g/mL were prepared. The mass (m) of the solution is:

150.0 mL \times \frac{1.02g}{mL}  = 153 g

Given the specific heat capacity of the solution (c) is 4.184 J/g・°C, we can calculate the change in the temperature (ΔT) of the solution using the following expression.

Qa = c \times m \times \Delta T\\\\\Delta T = \frac{Qa}{c \times m} = \frac{3.76 \times 10^{3}J  }{\frac{4.184J}{g.\° C }  \times 153g} = 5.87 \° C

When 3.66 g of KOH (∆Hsol = -57.6 kJ/mol) is dissolved in 150.0 mL of solution, it causes a temperature change of 5.87 °C.

Learn more: brainly.com/question/4400908

7 0
2 years ago
The question is below
pogonyaev
The reaction that has the greatest tendency to be reversed in an spontaneous redox reaction is that whose forward standard reduction potential is the lowest (mos negative) one because that means that the reversed reaction will have the highest (most positive) standard reduction potential.

So, the answer is Cr(3+) + 3e-    ---> Cr(s) with Eo = -0.91 V, whose reversed reaction is Cr(s) - 3e-         ---> Cr (3+) with Eo = +0.91 V.

Answer: the second option Cr(3+) + 3e-    ---> Cr(s)  Eo = -0.91 V
5 0
3 years ago
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