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3 years ago

Explain the changes that take place at the molecular level when a substance is superheated or supercooled ?

1 answer:

4 0

Only gas or vapor can be superheated. Use water as an example. Water at sea level boils at 212 degrees F. When heated to 212 degrees F, the molecules that make up water are moving at a high enough speed that they overcome the air pressure above the water. And for supercooled only liquids or solids can be supercooled for example Liquid water at sea level has a saturation (boiling) temperature of 212 degrees F. If we were to add heat to the saturated water, it would first boil away with no change in temperature (remember latent heat?) and then become superheated if still more heat were added to the vapor (steam) after it had all turned to a vapor.

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Over the years, the thermite reaction has been used for welding railroad rails, in incendiary bombs, and to ignite solid-fuel ro

melamori03 [73]

Answer: The mass of nickel (II) oxide and aluminium that must be used is 18.8 g and 4.54 g respectively.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For nickel:

Given mass of nickel = 14.8 g

Molar mass of nickel = 58.7 g/mol

Putting values in equation 1, we get:

$\text{Moles of nickel}=\frac{14.8g}{58.7g/mol}=0.252mol$

For the given chemical reaction:

$3NiO(s)+2Al(s)\rightarrow 3Ni(l)+Al_2O_3(s)$

For nickel (II) oxide:

By Stoichiometry of the reaction:

3 moles of nickel are produced from 3 moles of nickel (II) oxide

So, 0.252 moles of nickel will be produced from $\frac{3}{3}\times 0.252=0.252mol$ of nickel (II) oxide

Now, calculating the mass of nickel (II) oxide by using equation 1:

Molar mass of nickel (II) oxide = 74.7 g/mol

Moles of nickel (II) oxide = 0.252 moles

Putting values in equation 1, we get:

$0.252mol=\frac{\text{Mass of nickel (II) oxide}}{74.7g/mol}\\\\\text{Mass of nickel (II) oxide}=(0.252mol\times 74.7g/mol)=18.8g$

For aluminium:

By Stoichiometry of the reaction:

3 moles of nickel are produced from 2 moles of aluminium

So, 0.252 moles of nickel will be produced from $\frac{2}{3}\times 0.252=0.168mol$ of aluminium

Now, calculating the mass of aluminium by using equation 1:

Molar mass of aluminium = 27 g/mol

Moles of aluminium = 0.168 moles

Putting values in equation 1, we get:

$0.168mol=\frac{\text{Mass of aluminium}}{27g/mol}\\\\\text{Mass of aluminium}=(0.168mol\times 27g/mol)=4.54g$

Hence, the mass of nickel (II) oxide and aluminium that must be used is 18.8 g and 4.54 g respectively.

4 0

3 years ago

Which best describes nuclear fission

Firlakuza [10]

Nuclear fission is either a nuclear reaction or radio active decay process in which nucleus (the center) of an atom splits into smaller parts called nuclei. This is an extremely exothermic reaction (i.e a reaction which produces heat) resulting into release of massive amount of energy in the form of heat and sometimes light. The reaction produces much more energy as compared to a similar mass of a conventional fuel, such as Petrol/Kerosene/Petroleum Gas etc. This makes Nuclear fission an extremely dense and at times very destructive source of energy. Some common elements capable of Nuclear fission are Uranium, Plutonium etc. Though in modern days Nuclear Fission are finding application in being a source of energy (such as a Nuclear power plant), but they are also used in destructive format as Nuclear Bombs and it's one of the top most imminent threats to the existence of humanity in future (in the event of a Nuclear war).

7 0

3 years ago

Read 2 more answers

The man who developed the concept that light is emitted and absorbed in bundles or packets was:

ludmilkaskok [199]

Planck suggested that light/energy was absorbed/released in certain amounts, called quanta.

3 0

3 years ago

Read 2 more answers

Cobalt-60 is produced by neutron activation. in this process, one neutron is absorbed by the nucleus of the parent isotope. what

kkurt [141]

The parent isotope is cobalt-59 (see the picture below).

The mass number is 59 and atomic number is 27 of the parent isotope.

Neutron activation is the process in which atomic nucleus capture free neutron or neutrons.

Cobalt-60 is produced in nuclear reactors in process of neutron activation from parent isotope cobalt-59 (see the picture below).

Atomic number (Z) is total number of protons and mass number (A) is total number of protons and neutrons in a nucleus.

Cobalt-59 and cobalt-60 are the isotopes of chemical element cobalt.

Isotopes are chemical elements with same atomic number (Z), but different mass number (different number of neutrons).

More about isotopes: brainly.com/question/364529

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6 0

2 years ago

Britney added 0.05 moles of copper(II) nitrate solution to 0.1 moles of sodium hydroxide solution and

Rama09 [41]

The percent yield of copper hydroxide is 84%

<h3>Stoichiometry</h3>

From the question, we are to determine the percent yield of copper hydroxide

First, we will determine the theoretical mass

From the given balanced chemical equation, we have

Cu(NO₃)₂ + 2NaOH -- Cu(OH)₂ + 2NaNO₃

This means,

1 mole of copper(II) nitrate reacts with 2 moles of sodium hydroxide to produce 1 mole of copper hydroxide

Therefore,
0.05 mole of copper(II) nitrate reacts with 0.1 mole of sodium hydroxide to produce 0.05 mole of copper hydroxide

The theoretical number of moles of copper hydroxide that is produced is 0.05 mole

Now, for the theoretical mass

Using the formula,

Mass = Number of moles × Molar mass

Molar mass of copper hydroxide = 97.56 g/mol

Then,

Theoretical mass = 0.05 × 97.56

Theoretical mass of copper of hydroxide produced is = 4.878 g

Now, for the percent yield of copper hydroxide

Percent yield is given by the formula,

$Percent\ yield = \frac{Actual\ yield}{Theoretical\ yield} \times 100\%$

Then,

$Percent\ yield\ of\ copper\ hydroxide= \frac{4.1}{4.878}\times 100\%$

$Percent\ yield\ of\ copper\ hydroxide= 84\%$

Hence, the percent yield of copper hydroxide is 84%.

Learn more on Stoichiometry here: brainly.com/question/9372758

7 0

3 years ago