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2 years ago

Please help 15 points

Chemistry

1 answer:

sleet_krkn [62]2 years ago

7 0

<h3>Further explanation </h3>

Given

Atomic symbol

<h3> Required </h3>

Atomic composition

Solution

Atomic number = number of protons = number of electrons

Mass Number (A) is the sum of protons and neutrons

Number of protons and Number of Neutrons in nucleus

Number of electrons in the shell

From the picture:

protons = 3

neutrons = 4

electrons = 3

atomic number = protons = electrons = 3

mass number = protons + neutrons = 3+4 = 7

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Isotopes are atoms of the same element that have the same chemical property but may not have the same physical properties A true

Romashka-Z-Leto [24]

Answer:

false

Explanation:

Atoms of the same element that differ in their numbers of neutrons are called isotopes. Many isotopes occur naturally. ... Different isotopes of an element generally have the same physical and chemical properties because they have the same numbers of protons and elec

7 0

3 years ago

A 0.15 m solution of chloroacetic acid has a ph of 1.86. What is the value of ka for this acid?

dem82 [27]

Answer: $1.67\times 10^{-3}$

Explanation:

$ClCH_2COOH\rightarrow ClCH_2COO^-+H^+$

cM 0 0

$c-c\alpha$ $c\alpha$ $c\alpha$

So dissociation constant will be:

$K_a=\frac{(c\alpha)^{2}}{c-c\alpha}$

Given: c = 0.15 M

pH = 1.86

$K_a$ = ?

Putting in the values we get:

Also $pH=-log[H^+]$

$1.86=-log[H^+]$

$[H^+]=0.01$

$[H^+]=c\times \alpha$

$0.01=0.15\times \alpha$

$\alpha=0.06$

As $[H^+]=[ClCH_2COO^-]=0.01$

$K_a=\frac{(0.01)^2}{(0.15-0.15\times 0.06)}$

$K_a=1.67\times 10^{-3]$

Thus the vale of $K_a$ for the acid is $1.67\times 10^{-3}$

4 0

3 years ago

A) Calculate the osmotic pressure difference between seawater and fresh water. For simplicity, assume thatall the dissolved salt

never [62]

Answer:

a) Δπ = 1.264 atm

b) W = 128 joules

c) ΔH >> W ( a factor greater than 17,000 )

Explanation:

a) The osmotic pressure, π , is determined by :

π = nRT/V, where n= moles of solute

R= 0.0821 Latm/kmol

T = 300 K

calling π(sw) osmotic pressure for for sea water and π (fw) for fresh water,

salinity of sea water = 3.5 g / 1L water (assuming only NaCl for the salts)

salinity of fresh water = 0.5 parts per thousand (range: 0- 0.5 ppt)

πsw = (3.5 g/58.44 g/mol) (0.0821 Latm/Kmol) (300 K ) /1 L = 1.475 atm

πfw = (0.5 g/58.44 g/mol) (0.0821 Latm/Kmol) (300 K ) /1 L = 0.211 atm

d water = 1 g/cm³

Δ π = (1.475 - 0.211) = 1.264 atm

b) W = Δπ V = 1.426 atm x 1L = 1.43 L-atm

1 L-atm = 101.33 j

W = 101.33 j/ Latm x 1.43 Latm = 128 joules

c) ΔH = Q₁ + nΔH vap, where

Q₁ = heat required to bring the solution from 300 K to boiling, 373 K

ΔH vap = heat of vaporization

Q = mCΔT = 1000 g x 4.186 j x 73 K = 305.6 j = 0.3056 kj

ΔH vap = (1000 g/ 18 g/mol ) 40.7 kj/mol = 2,261 kj

ΔH = 0.3056 kj + 2,261 kj = 2,261.3 kj

Note = Q << ΔH vap and we could have neglected it.

This result shows why nobody talks about evaporation of sea water to produce fresh water ΔH >> W

6 0

3 years ago

What is the minimum (non-zero) thickness of a benzene (n = 1.501) thin film that will result in constructive interference when v

ad-work [718]

Explanation:

At each reflecting surface (benzene and glass) there will be 180 degree phase change.

Now, for constructive interference the optical path in benzene is $\lambda$ .

Formula to calculate thickness of a benzene thin film is as follows.

Optical path length through benzene ( $\lambda$ ) = $2 \times n \times d$

Hence, substituting the given values into the above formula as follows.

Optical path length through benzene = $2 \times n \times d$

d = $\frac{\text{Optical path length through benzene}}{2 \times n}$

= $\frac{\lambda}{2 \times n}$

= $\frac{615 \times 10^{-9}}{2 \times 1.501}$ (as 1 nm = $10^{-9}m$

= 204.9 m

Thus, we can conclude that minimum thickness of benzene is 204.9 m.

4 0

3 years ago

An aluminum can (Al) has a mass of 15.8 grams. How many atoms of aluminum are in the can?

Naddik [55]

Answer:

i think this is the answer you can try it tho...

Explanation:

Notice that the value 12.01 grams of natural carbon is the same as the atomic mass value (12.01 amu). It also tells us that 26.98 grams of aluminum contains exactly 6.022 x 1023 atoms of aluminum.

5 0

2 years ago