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3 years ago

When was the first published textbook containing a table identifying the first 33 elements

1 answer:

5 0

1789 -- raité élémentaire de chimie is a textbook written by Antoine Lavoisier published in 1789 and translated into English by Robert Kerr in 1790 under the title Elements of Chemistry

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Dichotomous Keys are used to identify organisms based on their observed characteristics. Dichotomous means..

BartSMP [9]

Dichotomous keys consist of a series of statements with two choices in each step that will lead users to the correct identification. So I believe your answer would be A.

7 0

3 years ago

0.53g of acetanilide was subjected to kjeldahl determination and the ammonia produced was collected in 50cm3 of 0.50M of h2so4.o

Lady bird [3.3K]

Answer:

10.57% of N in acetanilide

Explanation:

All nitrogen in the sample is converted in NH₃ in the Kjeldahl determination. The NH₃ reacts with H₂SO₄ as follows:

2NH₃ + H₂SO₄ → 2NH₄⁺ + SO₄²⁻

The acid in excess in titrated with Na₂CO₃ as follows:

Na₂CO₃ + H₂SO₄ → Na₂SO₄ + H₂O + CO₂

To solve this question we must find the moles of sodium carbonate = Moles of H₂SO₄ in excess. The added moles - Moles in excess = Moles of sulfuric acid that reacts:

Moles Na₂CO₃ anf Moles H₂SO₄ in excess:

0.025L * (0.05mol / L) = 1.25x10⁻³ moles Na₂CO₃ / 0.01360L =

0.09191M * 0.250L = 0.0230 moles H₂SO₄ in excess.

Moles H₂SO₄ added:

0.050L * (0.50mol / L) = 0.0250 moles H₂SO₄ added

Moles that react:

0.0250 moles - 0.0230 moles = 0.0020 moles H₂SO₄

Moles of NH₃ = Moles N:

0.0020 moles H₂SO₄ * (2mol NH₃ / 1mol H₂SO₄) = 0.0040 moles NH₃ = Moles N

mass N and mass percent:

0.0040 moles N * (14g / mol) = 0.056gN / 0.53g * 100 =

<h3>10.57% of N in acetanilide</h3>

7 0

3 years ago

If 25.5g of sodium thiosulphate was dissolved in 40g of distilled water at 25°C,

zhenek [66]

Answer:

Formula: Na2S2O3

we get solubility.

Divide the mass of the compound by the mass of the solvent and then multiply by 100 g to calculate the solubility in g/100g .

Solution given:

mass of sodium thiosulphate [m1]=25.5g

mass of water [m2]=40g

at temperature [t]=25°C

we have

solubility in g/dm^3 : $\frac{solute in gram}{solvent in gram} *100$

= $\frac{25.5}{40}*100$
=63.75g /litre=63.75g/dm³

solubility in g/dm^3 :63.75g/dm³

now

solubility of the solute in mol/dm^3=:63.75g/dm³/178=0.4 mol/dm³

6 0

3 years ago

Why would an aqueous solution of a strong electrolyte conduct electricity better than an aqueous solution of a weak electrolyte?

Virty [35]

The answer is B because the more ions the more electrolytes it has

4 0

4 years ago

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What was Bohr's model of the atom?

saveliy_v [14]

Answer:

In atomic physics, the Bohr model or Rutherford–Bohr model, presented by Niels Bohr and Ernest Rutherford in 1913, is a system consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar System, but with attraction provided by electrostatic forces in place of gravity.

Explanation:

4 0

3 years ago

Read 2 more answers