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3 years ago

Which of the following is true about elements?

Chemistry

1 answer:

Sophie [7]3 years ago

4 0

C. Elements combine to form compounds in organisms and nonliving substances

Explanation:

Elements combine to form compounds in both living and non-living organisms.

Elements are distinct substances that cannot be split-up into simpler substances.
Elements are made up of only one kind of atoms
Elements are pure substances.
When elements combine, they form compounds.
Compounds are found in all matter.

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You are given a cube of lead that is 1.000 cm on each side. The density of lead is 11.35. How many atoms of lead are in the samp

aliya0001 [1]

<u>11.35 g</u><u> </u><u>atoms </u><u>of lead are in the sample.</u>

What does density mean?

The density of an area refers to the quantity of things—which may include people, animals, plants, or objects—there are in it.
Divide the number of objects by the area's measurement to determine density.
A country's population density is calculated by dividing its total population by its area, expressed in square kilometers or miles.

We can calculate the volume of the cube by cubing the side of the cube.

Volume of cube = ( 1.000 cm)³

= 1.000 cm³

We can now determine the amount of lead in the cube by multiplying by the density. Because we know we have a 1.000 cubic centimeter and that lead has a density of 11.35 grams per cubic centimeter, we have 11.35 grams of lead.

= ( 1.000 cm³) ( 11.35 $\frac{g}{cm^{3} }$ )

= 11.35 g

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3 0

2 years ago

PLEASE I NEED HELP ASAP!!!!

miv72 [106K]

The percent yield of the calcium hydroxide is 84.5%.

<h3>What is stoichiometry?</h3>

Stoichiometry enables us to obtain the mass of a substance form the equation of the reaction.

The equation of the reaction is;

CaCO3 + 2HCl -----> CaCl2 + CO2 + H2O

Number of moles of X = 40.0 grams/100 g/mol = 0.4 moles

Number of moles of HCl = 850/1000 * 1 M = 0.85 moles

If 1 mole of CaCO3 reacts with 2 moles of HCl

0.4 moles of CaCO3 reacts with 0.4 moles * 2 moles/1 mole

= 0.8 moles of HCl

Hence X is the limiting reactant.

The reaction is 1:1 then the amount of CO2 produced is 0.4 moles

Mass of CO2 = 0.4 CO2 * 44 g/mol = 17.6 g

2) The reaction equation is; 2NaOH + CaCO3 ---> Ca(OH)2 + Na2CO3

Number of moles of X = 25.0 grams/100 g/mol = 0.25 moles

Number of moles of NaOH= 40/1000 L * 2 M = 0.08 moles

If 1 mole of X reacts with 2 moles of NaOH

0.25 moles reacts with 0.25 moles * 2 moles /1 mole

= 0.5 moles

NaOH is the limiting reactant

2 moles of NaOH produces 1 mole of CO2

0.08 moles of NaOH produces 0.08 moles * 1 mole/2 moles

= 0.04 moles of CO2

Theoretical yield of CO2 = 0.04 moles of CO2 * 74 g/mol = 2.96 g

Percent yield = 2.5 g/ 2.96 g * 100

= 84.5%

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5 0

2 years ago

12.23 g of ammonia (NH3) are dissolved in enough water to make 560.0 mL of solution. How many moles of NH3 are added to the wate

Karolina [17]

Answer:

0.719 moles of NH₃

Explanation:

Molar mass of ammonia 17 g/mol

Mass of amonia = 12.23 g

Mass / Molar mass = Moles

12.23 g / 17 g/mol = 0.719 moles

4 0

3 years ago

What can occur in physical change ?

Alexandra [31]

Within a physical change, an element can change forms, such as going from solid to a liquid through melting. Color change can also occur during a physical change. Physical changes are very different from chemical changes. In a chemical change the element itself changes into something else within a reaction, such as combustion (burning).

Hope this helped

5 0

3 years ago

The following equation is balanced according to the Law of Conservation of Mass:

igor_vitrenko [27]

The answer would be:
True

6 0

3 years ago