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3 years ago

How many elements had been discovered by 1860

1 answer:

5 0

60 elements! I don't exactly know every element known, so if you are asking that, please tell us, but what I do know is that there were 60 elements in the periodic table by 1860.

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Diseases can spread rapidly in cities. If a disease kills many people in a city but fewer in a rural area, this is an example of

Inga [223]

Answer:

Density independent factor

Explanation:

in dense areas where people livein very close and tight spaces

5 0

3 years ago

If a solid has a density of 4.0 g/cm^3, what volume of the solid has a mass<br> of 24 g? Show work.

Mrrafil [7]

Answer:

<h2>Volume = 6 cm³</h2>

Explanation:

Density of a substance is given by

$Density = \frac{mass}{volume}$

From the question

Density = 4.0 g/cm³

mass = 24g

Substitute the values into the above formula and solve for the volume

That's

$4 = \frac{24}{v} \\4v = 24$

Divide both sides by 4

v = 6

We have the final answer as

<h3>Volume = 6 cm³</h3>

Hope this helps you

8 0

3 years ago

18 An important environmental consideration is the appropriate disposal of cleaning solvents. An environmental waste treatment c

Katyanochek1 [597]

Answer:

a) Percentage by mass of carbon: 18.3%

Percentage by mass of hydrogen: 0.77%

b) Percentage by mass of chlorine: 80.37%

c) Molecular formula: $C_{2} H Cl_{3}$

Explanation:

Firstly, the mass of carbon must be determined by using a conversion factor:

$0.872g CO _{2} *\frac{12g C}{44g CO_{2} } = 0.238g CO_{2}$

The same process is used to calculate the amount of hydrogen:

$0.089g H_{2}O*\frac{2g H}{18g H_{2}O } = 0.010g H$

The percentage by mass of carbon and hydrogen are calculated as follows:

%C $\frac{0.238g}{1.3g} *100%$ = 18.3%

%H $\frac{0.010g}{1.3g} *100%$ =0.77%

From the precipation data it is possible obtain the amount of chlorine present in the compound:

$1.75 AgCl*\frac{35.45g Cl}{143.45g AgCl}$ = 0.43g AgCl

Let's calculate the percentage by mass of chlorine:

%Cl= $\frac{0.43g}{0.535g} * 100%$ = 80.37%

Assuming that we have 100g of the compound, it is possible to determine the number of moles of each element in the compound:

$18.3g C*\frac{1mol C}{12g C} = 1.52mol C$

$0.77g H*\frac{1mol H}{1g H} = 0.77mol H$

$80.37gCl*\frac{1molCl}{35.45g Cl} = 2.27mol Cl$

Dividing each of the quantities above by the smallest (0.77mol), the subscripts in a tentative formula would be

$C=\frac{1.52}{0.77} = 1.97$ ≈ 2

$H = \frac{0.77}{0.77} = 1$

$Cl =\frac{2.27}{0.77}=2.94$ ≈3

The empirical formula for the compound is:

$C_{2} H Cl_{3}$

The mass of this empirical formula is:

mass of C + mass of H + mass of Cl= 24g +1+ 106.35 =131.35g

This mass matches with the molar mass, which means that the supscript in the molecular formula are the same of the empirical one.

5 0

3 years ago

Check all items common to bases.<br> minerals<br> metal<br> gas<br> H+<br> OH-<br> nitrogen

Darya [45]

OH- is common to bases.

Explanation:

The base is a is an ionic compounds which when placed in aqueous solution dissociates in to a cation and an anion OH-.

The presence of OH- in the solution shows that the solution is basic or alkaline.

From Bronsted and Lowry concept base is a molecule that accepts a proton for example in NaOH, Na is a proton donor and OH is the proton acceptor.

A base accepts hydrogen ion and the concentration of OH is always higher in base.

There is a presence of conjugate acid and conjugate base in the Bronsted and Lowry acid and base.

Conjugate acid is one which is formed when a base gained a proton.

Conjugate base is one which is formed when an acid looses a proton.

And from the Arrhenius base Theory, the base is one that dissociates in to water as OH-.

8 0

3 years ago

The percent composition of calcium is ?

DochEvi [55]

Answer: 40.1%

Explanation: The mass of calcium in this compound is equal to 40.1 grams because there's one atom of calcium present and calcium has an atomic mass of 40.1 . The molar mass of the compound is 100.1 grams. Using the handy equation above, we get: Mass percent = 40.1 g Ca⁄100.1 g CaCO3 × 100% = 40.1% Ca.

5 0

3 years ago