If 175 undecayed nuclei remained from a sample of 2800 nuclei, how many half-lives has passed? *

What is the volume in liters of 3.80 moles of CO2gas at STP?

pantera1 [17]

Answer:

V = 85.2

Explanation:

STP = 273K and 1 atm

Considering what we know about STP, we get the moles, temperature, and pressure. Using the ideal gas law we can find the volume (PV = nRT). Plug in our variables: (1 * V = 3.80 * R * 273). Since we are dealing with atm and not kPA or mmHg, we use the constant for atm (0.0821) which we use for R. (So.. now our equation is 1 * V = 3.80 * 0.0821 * 273). We now multiply the right side to get 85.17054. So... V = 85.2 considering sigificant figures (this is the part where I am the least sure of, since I havent done sig figs in a while)

8 0

3 years ago

The elemental analysis of an organic solid extracted from gum arabic (a gummy substance used in adhesives, inks, and pharmaceuti

Evgesh-ka [11]

Answer:

The molar mass of the organic solid is 120.16 g/mol.

The molecular formula of an organic solid is $C_4H_8O_4$

Explanation:

Let the molecular mass of an organic solid be $C_xH_yO_z$

$\Delta T_b=K_b\times m$

$Delta T_b=K_b\times \frac{\text{Mass of solid}}{\text{Molar mass of solid}\times \text{Mass of diphenyl in Kg}}$

where,

$\Delta T_f$ =Elevation in boiling point = $=1.5^oC$

Mass of organic solid= 0.561 g

Mass of diphenyl = 24.9 g = 0.0249 kg (1 kg = 1000 g)

$K_b$ = boiling point constant = 8.00 °C/m

m = molality

Now put all the given values in this formula, we get

$1.5^oC=8.00 ^oC/m\times \frac{0.561 g}{\text{Molar mass of solid}\times 0.0249 kg}$

${\text{Molar mass of solid}}=120.16 g/mol$

$\%=\frac{\text{Number of atoms}\times \text{mass of an atom}}{\text{molas mass of compound}}\times 100$

Percentage of carbon in an organic solid = 40.0%

$40\%=\frac{x\times 12 g/mol}{120.16 g/mol}\times 100$

x = 4.0

Percentage of hydrogen in an organic solid = 6.7%

$6.7\%=\frac{y\times 1 g/mol}{120.16 g/mol}\times 100$

y = 8.0

Percentage of hydrogen in an organic solid = 6.7%

$53.3\%=\frac{x\times 12 g/mol}{120.16 g/mol}\times 100$

y = 4.0

The molecular formula of an organic solid is $C_4H_8O_4$

8 0

3 years ago

someone pls help me with my chemistry test plsss my teacher changes the questions so I can't search them up. its 21 questions so

shusha [124]

Answer:

Correct option is

B

5 liters of CH

4

(g)NO

2

at STP

No. of molecules=

22.4

5

mol=

22.4

5

×N

A

molecules

A) 5ℊ of H

2

(g)

No. of moles=

2

5

mol=

2

5

×N

A

molecules

B) 5l of CH

4

(g)

No. of moles of CH

4

=

22.4

5

mol=

22.4

5

N

A

molecules

C) 5 mol of O

2

=5N

A

O

2

molecules

D) 5×10

23

molecules of CO

2

(g)

Molecules of 5l NO

2

(g) at STP=5l of CH

4

(g) molecules at STP

Therefore, option B is correct.

7 0

3 years ago

a molecule of two nitrogen atoms and four oxygen atoms what is the molecule formula for this compound

kiruha [24]

The formula would be N2O4

6 0

4 years ago

Read 2 more answers

2. Calculate the atomic mass of an element that has two isotopes, each with 50.00% abundance. One isotope has a mass of 63.00 am

melamori03 [73]

Answer:

The atomic mass of element is 65.5 amu.

Explanation:

Given data:

Abundance of X-63 = 50.000%

Atomic mass of X-63 = 63.00 amu

Atomic mass of X-68 = 68.00 amu

Atomic mass of element = ?

Solution:

Abundance of X-68 = 100-50 = 50%

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass) / 100

Average atomic mass = (50×63)+(50×68) /100

Average atomic mass = 3150 + 3400 / 100

Average atomic mass = 6550 / 100

Average atomic mass = 65.5 amu.

The atomic mass of element is 65.5 amu.

7 0

3 years ago