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arsen [322]
3 years ago
10

An atom of 40 18 Ar has a nucleus that contains a total of

Chemistry
2 answers:
melisa1 [442]3 years ago
5 0
Atoms are composed of protons, electrons, and neutrons. so, answer D can be discarded because it is not what atoms are made of. 

40 and 18 represent the atomic mass and atomic number respectively. the atomic number presents the number of protons. so there are 18 protons. the number of neutrons can be determined by taking the atomic mass minus the atomic number. neutrons= 40-18= 22 neutrons.

so the answer is B

Answer A may be correct if we assume the atom is neutral. in a neutral atom, the number of protons is the same as the number of electrons. but the electrons are not in the nucleus but orbiting it. the question specified the nucleus.
Cloud [144]3 years ago
4 0
The correct answer is b, 18 protons
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The rate constant for a certain reaction is k = 4.70×10−3 s−1 . If the initial reactant concentration was 0.700 M, what will the
Lynna [10]

Answer:

Therefore the concentration of the reactant after 4.00 minutes will be 0.686M.

Explanation:

The unit of k is s⁻¹.

The order of the reaction = first order.

First order reaction: A first order reaction is  a reaction in which the rate of reaction depends only the value of the concentration of the reactant.

-\frac{d[A]}{dt} =kt

[A] = the concentration of the reactant at time t

k= rate constant

t= time

Here k= 4.70×10⁻³ s⁻¹

t= 4.00

[A₀] = initial concentration of reactant = 0.700 M

-\frac{d[A]}{dt} =kt

\Rightarrow -\frac{d[A]}{[A]}=kdt

Integrating both sides

\Rightarrow\int -\frac{d[A]}{[A]}=\int kdt

⇒ -ln[A] = kt +c

When t=0 , [A] =[A₀]

-ln[A₀]  = k.0 + c

⇒c= -ln[A₀]  

Therefore

-ln[A] = kt - ln[A₀]

Putting the value of k, [A₀] and t

- ln[A] =4.70×10⁻³×4 -ln (0.70)

⇒-ln[A]=  0.375

⇒[A] = 0.686

Therefore the concentration of the reactant after 4.00 minutes will be 0.686M.

5 0
3 years ago
Compound Y has the elements C, H, N and O. It's exact mass is 91.0425. Answer the following questions. Isotope Exact Mass 1H 1.0
Talja [164]

Answer:

Six C atoms (C₆); five H atoms (H₅); one N atom (N); no O atoms

Explanation:

The rule of 13 states that the formula of a compound is a multiple n of 13 (the molar mass of CH) plus a remainder r.

MF = CₙHₙ₊ᵣ

Y has a molecular mass of 91 u

91/13 =7r0

The formula can't be C₇H₇ because a hydrocarbon must have an even number of H atoms,

The odd mass and the odd number of H atoms make it reasonable to add an N atom and subtract CH₂ (CH₂ = 14):

C₇H₇ + N - CH₂ = C₆H₅N

Check:

6C = 6 × 12.000 = 72.000 u

5H = 5 ×   1.008 =   5.040

1N =  1 × 14.003 =  <u>14.003    </u>

             TOTAL =   91.043 u

This is excellent agreement with the observed mass of 91.0425 u.

There are six  C atoms (C₆)

There are five H atoms (H₅)

There is    one N atom   (N)

There are no   O atoms.

4 0
3 years ago
If D+2 would react with E!, what do you predict to be the formula?
kherson [118]

Answer:

I think the answers D. Hope this helps you.

Explanation:

6 0
3 years ago
Is Naci a metal or none metel
Schach [20]

Answer:

Salt (NaCl) is an ionic bond that consists of Sodium (Na) which is a metal with positive charge combines with Chlorine (Cl), a nonmetal with a negative charge.

Explanation:

3 0
3 years ago
Why did rutherford conclude from his gold foil experiment that an atom is mostly comprised of empty space?
Nady [450]
'cause many alpha-particle goes without any deflection........
6 0
4 years ago
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