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elena55 [62]
3 years ago
13

Mendeleev’s periodic table shocked the scientific community because it contradicted earlier findings about element mass and prop

erties. True or False?
Chemistry
2 answers:
mash [69]3 years ago
8 0

False,

The most amazing part of Mendeleev’s periodic table was that he left blank spaces for the elements which were yet to be discovered. He predicted the atomic mass and chemical properties of these yet to be discovered elements.



Naddika [18.5K]3 years ago
4 0

Answer:

FALSE

Explanation:

The organization of the elements was presented by Mendeleev to the scientific community, and gave rise to what we know today as the "Periodic Table", in which the elements are arranged in horizontal rows, according to the growing atomic masses, and also in vertical columns, with elements of similar properties. With Mendeleev's Periodic Table of Chemical Elements, some questions about the constitution of our material universe began to be answered by chemists, as were the simple substances that constituted it. Through the periodic table, one can be sure for the first time that matter was not made up of a single element. Therefore, the table confirmed suspicions and helped the chemists to mark their searches.

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If a concentrated solution of acetic acid is 99.5 % HC2 H3 O2 and has a density of 1.05 g/mL, what is the concentration of this
cluponka [151]

Answer:

[CH₃COOH] = 17.4 M

Explanation:

Acetic acid → CH₃COOH

Molar mass → 60 g/mol

99.5% is percent by mass concentration. It means that 99.5 grams of solute are contained in 100g of solution.

Density → 1.05 g/mL. This data is always referred to solution, not solute!.

We determine solution's volume:

1.05 g/mL = 100 g / V → V = 100 g /1.05 g/mL → 95.2 mL

Now we know, that 99.5 g of acetic acid are contained in 95.2 mL

Let's convert to mmoles → 99.5 g / 60 g/mol = 1.66 moles

We convert solution's volume to L → 95.2 mL . 1L / 1000 mL = 0.0952 L

M (mol/L) = 1.66 mol / 0.0952 L = 17.4 M

5 0
3 years ago
Explain the following terms Sublimation
weqwewe [10]

Answer:

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. ... The reverse process of sublimation is deposition or desublimation, in which a substance passes directly from a gas to a solid phase.

8 0
3 years ago
How many half-lives are required for the concentration of reactant to decrease to 1.56% of its original value?4247.56.56
neonofarm [45]

Answer:

6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.

Explanation:

Using integrated rate law for first order kinetics as:

[A_t]=[A_0]e^{-kt}

Where,

[A_t] is the concentration at time t

[A_0] is the initial concentration

Given:

Concentration is decreased to 1.56 % which means that 0.0156 of [A_0] is decomposed. So,

\frac {[A_t]}{[A_0]} = 0.0156

Thus,

\frac {[A_t]}{[A_0]}=e^{-k\times t}

0.0156=e^{-k\times t}

kt = 4.1604

The expression for the half life is:-

Half life = 15.0 hours

t_{1/2}=\frac {ln\ 2}{k}

Where, k is rate constant

So,  

k=\frac {ln\ 2}{t_{1/2}}

\frac{4.1604}{t}=\frac {ln\ 2}{t_{1/2}}

t = 6\times t_{1/2}

<u>6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.</u>

6 0
4 years ago
Substances that can carry electric current under some conditions but not under others are called semiconductors.
Dmitry [639]
A semiconductor is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. Silicon is a very common element -- for example, it is the main element in sand and quartz.
8 0
3 years ago
If a solid is placed in a liquid and lots of bubbles are formed, is this a physical change? or is it a chemical change?
Leni [432]
It’s a chemical change!
4 0
3 years ago
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