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3 years ago

Need help on these please and thank you

Chemistry

1 answer:

Snowcat [4.5K]3 years ago

6 0

Statement:

The best way to measure the mass of an orange is to use a balance. You put the orange and the mass pieces in the same cup on the balance and find out how many centimeters it is. The mass of my orange was 145.

Explanation:

Problem 1

The student has not done a good job in measuring the weight of the orange. In fact, the has complicated his simple problem.

Reasons:

Using the mass pieces and the cup to find the weight of the orange is wrong approach.

He can easily place the orange on the balance and read off the weight.

Centimeters is a unit of length. What length is he measuring and recording?

The unit of weight is in newtons(N).

Mass is not read from a balance. A balance gives the weight of substance. Mass is different from weight.

Problem 2

Rewriting to paragraph to correct the errors:

The best way to measure the mass of an orange is to use a balance. You put the orange on the balance and find out how many newtons it is. The weight in newtons can be converted to mass in kilogram. The mass of my orange will be 145kg.

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2C8H18+25O2→16CO2+18H2O.

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Entropy means that _________.A. the quantity of usable energy declines with each transformationB. energy can be neither created

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Answer:

answer A

Explanation:

A) the quantity of usable energy declines with each transformation → True . Since the entropy increases , the amount of energy that can not be converted to useful energy increases and since the total amount of energy is conserved, the quantity of useful energy decreases.

B) energy can be neither created nor destroyed → False in the context of entropy , since the energy is conserved regardless of the changes in entropy (First law → conservation of energy vs second law → increase of entropy)

C) life should be impossible → False . Since the second law states that the entropy of the <u>universe </u>increases with time . Then the system (life) can experience a decrease in entropy at the expense of a larger increase in entropy of the surroundings ( so the net increase is positive)

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3 years ago

If the sample contained 2.0 moles of KClO3 at a temperature of 214.0 °C, determine the mass of the oxygen gas produced in grams

Westkost [7]

Answer : The mass of the oxygen gas produced in grams and the pressure exerted by the gas against the container walls is, 96 grams and 1.78 atm respectively.

Explanation : Given,

Moles of $KCl_3$ = 2.0 moles

Molar mass of $O_2$ = 32 g/mole

Now we have to calculate the moles of $MgO$

The balanced chemical reaction is,

$2KClO_3\rightarrow 2KCl+3O_2$

From the balanced reaction we conclude that

As, 2 mole of $KClO_3$ react to give 3 mole of $O_2$

So, 2.0 moles of $KClO_3$ react to give $\frac{2.0}{2}\times 3=3.0$ moles of $O_2$

Now we have to calculate the mass of $O_2$

$\text{ Mass of }O_2=\text{ Moles of }O_2\times \text{ Molar mass of }O_2$

$\text{ Mass of }O_2=(3.0moles)\times (32g/mole)=96g$

Therefore, the mass of oxygen gas produced is, 96 grams.

Now we have to determine the pressure exerted by the gas against the container walls.

Using ideal gas equation:

$PV=nRT\\\\PV=\frac{w}{M}RT\\\\P=\frac{w}{V}\times \frac{RT}{M}\\\\P=\rho\times \frac{RT}{M}$

where,

P = pressure of oxygen gas = ?

V = volume of oxygen gas

T = temperature of oxygen gas = $214.0^oC=273+214.0=487K$

R = gas constant = 0.0821 L.atm/mole.K

w = mass of oxygen gas

$\rho$ = density of oxygen gas = 1.429 g/L

M = molar mass of oxygen gas = 32 g/mole

Now put all the given values in the ideal gas equation, we get:

$P=1.429g/L\times \frac{(0.0821L.atm/mole.K)\times (487K)}{32g/mol}$

$P=1.78atm$

Thus, the pressure exerted by the gas against the container walls is, 1.78 atm.

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