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3 years ago

What contribution did Niels Bohr make to atomic theory?

Chemistry

1 answer:

Nikitich [7]3 years ago

6 0

Answer:

Explanation:

he showed that electrons occupy shells or energy levels around the nucleus.

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What element is necessary for a healthy eye

Salsk061 [2.6K]

The element necissary for an eye is plain vision, oxygen,

3 0

3 years ago

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

1. Why is it necessary to equalize the pressure(i.e, have the water level the same in each tube) before taking a volume reading?

Anna11 [10]

Answer:

If you contact water with a gas at a certain temperature and (partial) pressure, the concentration of the gas in the water will reach an equilibrium ('saturation') according to Henry's law.

Explanation:

This means: if you increase the pressure (e.g. by keeping the vial closed), the CO2 concentration will increase. So it simply depends what concentration you need for your assay: 'CO2-saturated' water at low pressure or 'CO2-saturated' water at high pressure.

3 0

3 years ago

The game of kickball begins with the ball being rolled toward a player. The player then kicks the ball across the field. What is

hammer [34]

Answer:

C. The Speed of the ball depends on the force used to kick it.

Explanation:

6 0

3 years ago

Read 2 more answers

Two solid blocks are HEATED to the temperatures show. The blocks are placed so they touch. Which diagram shows the DIRECTION HEA

Setler [38]

Answer:

Heat flows from the block at high temperature to the one with lower temperature

Explanation:

The direction of heat flow is from a body at higher temperature to one with a lower temperature.

Temperature gradient determines the way and manner in which heat is dissipated.
As a system tend to increase entropy, it ensures that heat moves from hotter body to a colder body.
Heat movement here is by conduction as the body touches.
When both bodies reaches the same temperature, thermal equilibrium is established.

7 0

3 years ago