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3 years ago

8th Grade Checkpoint 1

Chemistry

1 answer:

Bad White [126]3 years ago

8 0

Answer:

Antimony, Sb, an atom contains 51 protons inside the nucleus and 51 electrons outside the nucleus.

Explanation:

Option “C” is correct because protons exist inside the nucleus and electrons exist outside the nucleus. Moreover, Sb has the number of protons 51 that is found in the nucleus and it has 51 electrons that exist outside the nucleus. However, the nucleus contains protons and neutrons while electrons exist outside of the nucleus. All the given options do not follow such condition therefore, all the statements are incorrect accept option 3rd.

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What two general products do combustion reactions create? *

Dimas [21]

It would be carbon dioxide and water.

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3 years ago

What might a physicit choose to study?

AlekseyPX

Thermodynamics, Nuclear Physics, Quantum Physics, Astronomy and Astrophysics

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3 years ago

Which topic is Eunice's project most likely about?

otez555 [7]

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3 years ago

A 52.9g sample of brass, which has a specific heat capacity of 0.375Â·JÂ·g^âˆ’1Â°C^âˆ’1, is put into a calorimeter (see sketch a

vaieri [72.5K]

Answer: 90.04°C

Explanation: <u>Calorimeter</u> is a device measures the amount of heat of a chemical or physical process. An ideal calorimeter is one that is well-insulated, i.e., prevent the transfer of heat between the calorimeter and its surroundings. So, the net heat change inside the calorimeter is zero:

$q_{1}+q_{2}=0$

Rearraging, it can be written as

$q_{1}=-q_{2}$

showing that the heat gained by Substance 1 is equal to the energy lost by Substance 2.

In our case, water is gaining heat, because its temperature has risen and so, brass is losing energy:

$q_{water}=-q_{brass}$

Calculating:

$m_{w}.c_{w}.\Delta T=-[m_{b}.c_{b}.\Delta T]$

$100.4.18.(18.4-15)=-[52.9.0.375.(18.4-T)]$

Note: final temperature is the same as the substances are in thermal equilibrium.

Solving:

418(3.4)= - 365.01 + 19.8375T

19.8375T = 1786.21

T = 90.04

The initial temperature for the sample of brass was 90.04°.

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2 years ago

What mass of bromine reacts with 16.2 g of aluminium?

Goshia [24]

For every, 3 Br- ions, 1 Al3+ ion reacts to form AlBr3.

Convert 16.2g of aluminum to moles:

16.2g Al / 27.0g per mol = 0.60 mols.

Based on the above ratio, 0.60 mols of Al will react with 1.8 mols of Br.

Convert 1.8 mols of Br to its mass:

1.8 mols Br × 79.9g per mol = 143.82g of Br.

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3 years ago