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3 years ago

A certain first-order reaction has a half-life of 20.0 minutes. How much time is required for this reaction to be 75% complete?

Chemistry

1 answer:

ryzh [129]3 years ago

3 0

Answer:

X = 2

Explanation:

As you know, the rate of a first-order reaction depends linearly on the concentration of a single reactant. The rate of a first-order reaction that takes the form

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How many grams of CaCl2 are in 250 mL of 2.0 M CaCl2?

Tom [10]

The answer is: " 56 g CaCl₂ " .
__________________________________________________________

Explanation:
__________________________________________________________
2.0 M CaCl₂ = 2.0 mol CaCl₂ / L ;

Since: "M" = "Molarity" (measurement of concentration);

= moles of solute per L {"Liter"} of solution.
__________________________________________________________
Note the exact conversion: 1000 mL = 1 L .

Given: 250 mL ;

250 mL = ? L ? ;

250 mL * (1 L / 1000 L) = (250/1000) L = 0.25 L .
___________________________________________________________

(2.0 mol CaCl₂ / L ) * (0.25L) = (2.0) * (0.25) mol = 0.50 mol CaCl₂ ;

We have: 0.50 mol CaCl₂ ; Convert to "g" (grams):

→ 0.50 mol CaCl₂ .
___________________________________________________________
1 mol CaCl₂ = ? g ?

From the Periodic Table of Elements:

1 mol Ca = 40.08 g

1 mol Cl = 35.45 g .

There are 2 atoms of Cl in " CaCl₂ " ;

→ Note the subscript, "2", in the " Cl₂ " ;
__________________________________________________________
So, to calculate the molar mass of "CaCl₂" :

40.08 g + 2(35.45 g) =

40.08 g + 70.90 g = 110.98 g ; round to 4 significant figures;

→ round to 111 g/mol .
__________________________________________________________
So:

→ 0.50 mol CaCl₂ = ? g CaCl₂ ? ;

→ 0.50 mol CaCl₂ * (111 g CaCl₂ / mol CaCl₂) ;

= (0.50) * (111 g) CaCl₂ ;

= 55.5 g CaCl₂ ;

 → round to 2 significant figures;

 → 56 g CaCl₂ .
___________________________________________________________
The answer is: " 56 g CaCl₂ " .
___________________________________________________________

6 0

3 years ago

Read 2 more answers

A sample of 1.000 g of a compound containing carbon and hydrogen reacts with oxygen at elevated temperature to yield 0.692 g H₂O

ollegr [7]

Answer :

(a) 1.000 g of compound containing carbon and hydrogen is, 0.922 g and 0.0769 g respectively.

(b) There is no other element present in the compound.

Explanation :

(a) Now we have to determine the masses of C and H in the sample.

The chemical equation for the combustion of hydrocarbon having carbon, hydrogen and oxygen follows:

$C_xH_y+O_2\rightarrow CO_2+H_2O$

where, 'x' and 'y' are the subscripts of Carbon and hydrogen respectively.

We are given:

Mass of $CO_2=3.381g$

Mass of $H_2O=0.692g$

We know that:

Molar mass of carbon dioxide = 44 g/mol

Molar mass of water = 18 g/mol

For calculating the mass of carbon:

In 44 g of carbon dioxide, 12 g of carbon is contained.

So, in 3.381 g of carbon dioxide, $\frac{12}{44}\times 3.381=0.922g$ of carbon will be contained.

For calculating the mass of hydrogen:

In 18 g of water, 2 g of hydrogen is contained.

So, in 0.692 g of water, $\frac{2}{18}\times 0.692=0.0769g$ of hydrogen will be contained.

Thus, 1.000 g of compound containing carbon and hydrogen is, 0.922 g and 0.0769 g respectively.

(b) Now we have to determine the compound contain any other elements or not.

Mass carbon + Mass of hydrogen = 0.922 g + 0.0769 g = 0.999 g ≈ 1 g

This means that there is no other element present in the compound.

3 0

3 years ago

Atoms of elements at the top of a group on the periodic table are smaller than the atoms of elements at the bottom of the group.

boyakko [2]

Answer:

Explanation:

As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased.

As the size of atom increases the ionization energy from top to bottom also decreases because it becomes easier to remove the electron because of less nuclear attraction and as more electrons are added the outer electrons becomes more shielded and away from nucleus.

On left side of periodic table atoms of metals are more reactive by loosing the electrons or we can say metals are more reactive by loosing the electrons so their reactivity increase down the group because of easily removal of electrons.

On right side of periodic table atoms of nonmetals are more reactive by gaining the electrons. As we move down the group nuclear attraction becomes smaller because of shielding thus electron are less attracted by nucleus and reactivity decreases.

7 0

3 years ago

Help! Which of these is a compound?: Carbon, chlorine, uranium, ammonia.

MrRa [10]

Ammonia is the compound.

4 0

3 years ago

KClO3 (s) KCl (s) + 02 (g) How do you balance this equation

Vitek1552 [10]

Answer:

2KCl(s) + 6O3O2

Explanation:

I think it's correct

7 0

3 years ago