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2 years ago

Give four different chemical meanings for the word element and an example of each

Chemistry

1 answer:

Naddika [18.5K]2 years ago

3 0

Answer ;

-An element is a substance containing only one type of atom, for example; H2 or 02 (consisting of atoms that all have the same number of protons).

-Microscopic, single atom of that element

-Macroscopic, sample of that element large enough to weigh on a balance

- A substance that cannot be broken down chemically; e.g; sodium metal,

Explanation;

-An element is a substance whose atoms all have the same number of protons: another way of saying this is that all of a particular element's atoms have the same atomic number. Elements are chemically the simplest substances and hence cannot be broken down using chemical reactions.

-An element is uniquely determined by the number of protons in the nuclei of its atoms.

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On a cool morning, Uyen’s breath can form a cloud when she breathes out. Which changes of state are most responsible for Uyen se

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The correct option is: VAPORIZATION AND CONDENSATION.

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2 years ago

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One brand of vinegar has a pH of 4.5. Another brand has a pH of 5.0. The equation for the pH of a substance is pH = –log[H+], wh

grigory [225]

[H+] in first brand:
4.5 = -log([H+])
[H+] = 10^(-4.5)

[H+] in second brand:
5 = -log[H+]
[H+] = 10^(-5)

Difference = 10^(-4.5) - 10^(-5)
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2 years ago

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An atom whose valence electrons conform to the octet rule is:

Readme [11.4K]

Answer: D. less likely to form any bond

Explanation:

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2 years ago

Element X is a radioactive isotope such that every 82 years, its mass decreases by half. Given that the initial mass of a sample

lesantik [10]

Answer: 17 years

Explanation:

Expression for rate law for first order kinetics for radioactive substance is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant

t = age of sample

a = let initial amount of the reactant

a - x = amount left after decay process

a) for completion of half life:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

$t_{\frac{1}{2}}=\frac{0.693}{k}$

$k=\frac{0.693}{82years}=8.4\times 10^{-3}years^{-1}$

b) for 8900 g of the mass of the sample to reach 7700 grams

$t=\frac{2.303}{8.4\times 10^{-3}}\log\frac{8900}{7700}$

$t=17years$

Thus it will take 17 years

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2 years ago

25. In the investigation shown the changes in heat of the copper is greater than the change in the heat of the water. What error

forsale [732]

Answer:

Heat lost to the surroundings

Heat lost to the thermometer

Explanation:

All changes in heat, or energy, can be explained. Many of the reactions or changes we see in the world involve the conversion of energy. For example as we heat up a substance (eg. water), the amount of energy we put in should give us an exact temperature. However, this is a "perfect world" scenario, and does not occur in real life. Whenever heat is added to a substance like water, we always need to account for the energy that is going to be lost. For example, heat lost to evaporation or even the effect of measuring the temperature with a thermometer (the introduction of anything including a thermometer will affect the temperature).

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2 years ago