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olya-2409 [2.1K]
3 years ago
11

When Mendeleev started his work on organizing the elements, about how many had

Chemistry
1 answer:
Talja [164]3 years ago
8 0

Answer:

About 60.

Explanation:

Mendeleev knew of 63 elements. He wrote their properties on cards and arranged them in order of atomic mass.

That's how he discovered that the properties of elements are periodic functions of their atomic masses.

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The density of Mg is 1.74g/cm3. The density of strontium is 2.60g/cm3. What would you expect the density of Ca to be?
Tomtit [17]

The density of Ca will be between that of Mg and Sr

Explanation:

Ca, Mg and Sr are group II elements. They are called alkali earth metals. The correct order of the elements in this group are: Be, Mg, Ca, Sr, Ba and Ra.

Density is an intensive property of matter which describes the amount of matter(mass) per volume of a substance.

  • Density varies proportionally with mass. The higher the mass, the higher its density.
  • On the periodic table, atomic mass which the number of protons and neutrons in the nucleus of an atom increases down the group.
  • This implies a progradation in the value of density down the group. Therefore one expects that the value of density of Ca will fall between that of Mg and Sr. It cannot be more than 2.6g/cm³ nor less than 1.74g/cm³.

Learn more:

density brainly.com/question/2658982

mass number brainly.com/question/2597088

#learnwithBrainly

                   

6 0
3 years ago
How will adding NaCl affect the freezing point of a solution?
lord [1]

Answer is: adding NaCl will lower the freezing point of a solution.

A solution (in this example solution of sodium chloride) freezes at a lower temperature than does the pure solvent (deionized water).

The higher the solute concentration (sodium chloride), freezing point depression of the solution will be greater.

Equation describing the change in freezing point:  

ΔT = Kf · b · i.

ΔT - temperature change from pure solvent to solution.

Kf - the molal freezing point depression constant.

b -  molality (moles of solute per kilogram of solvent).

i - Van’t Hoff Factor.

Dissociation of sodium chloride in water: NaCl(aq) →  Na⁺(aq) + Cl⁻(aq).

3 0
3 years ago
Read 2 more answers
Can someone please help I need help?!?!
anzhelika [568]

Answer:

a: 6 moles

b: 6.75 moles

c: 5 grams

Explanation:

a: mole ratio 2:3

b: mole ratio 2:3

c: mole ratio 2:2

7 0
3 years ago
What is the approximate percent by mass of potassium in KHCO3?
lozanna [386]

Answer:

The mass percent of potassium is 39%

Option C is correct

Explanation:

Step 1: Data given

Atomic mass of K = 39.10 g/mol

Atomic mass of H = 1.01 g/mol

Atomic mass of C = 12.01 g/mol

Atomic mass of O = 16.0 g/mol

Step 2: Calculate molar mass of KHCO3

Molar mass KHCO3 = 39.10 + 12.01 + 1.01 + 3*16.0

Molar mass KHCO3 = 100.12 g/mol

Step 3: Calculate mass percent of potassium (K)

%K = (atomic mass of K / molar mass of KHCO3) * 100%

%K = (39.10 / 100.12) * 100%

%K = 39.05 %

The mass percent of potassium is 39%

Option C is correct

8 0
3 years ago
Complete the equation for the conversion of sucrose into glucose <br> (1)C12H22O11 + H2O
Svetlanka [38]

Answer:

C₁₂H₂₂O₁₁ + H₂O     →    C₅H₁₂O₆ + C₆H₁₂O₆

Explanation:

Chemical equation:

C₁₂H₂₂O₁₁ + H₂O     →    C₅H₁₂O₆ + C₆H₁₂O₆

Source of sucrose:

Sucrose is present in roots of plants and also in fruits. It is storage form of energy. Some insects and bacteria use sucrose as main food. Best example is honeybee which collect sucrose and convert it into honey.

Monomers of sucrose and hydrolysis:

Sucrose consist of monomers glucose and fructose which are join together through glycosidic bond. Hydrolysis break the sucrose molecule into glucose and fructose. In hydrolysis glycosidic bond is break which convert the sucrose into glucose and fructose. Hydrolysis is slow process but this reaction is catalyze by enzyme. The enzyme invertase catalyze this reaction.

The given reaction also completely follow the law of conservation of mass. There are equal number of atoms of elements on both side of chemical equation thus mass remain conserved.

8 0
3 years ago
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