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3 years ago

An atom of sodium-23 (atomic number = 11) has a positive charge of +1. Given this information, how many

1 answer:

Elena-2011 [213]3 years ago

5 0

Proton number is the same as atomic number = 11
as electrons have a mass which is so small its counted as 0 and protons and neutrons relative mass is 1
the number of neutrons = 23- 11 = 12 neutrons
In a neutral atom the number of electrons= number of protons but here we have a +1 ion so there is one less electron then proton therefore the number of electrons = 10

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Describe the relative charge, relative mass and location of a proton.

Molodets [167]

The relative charge of a proton is +1. The relative mass of a proton is 1. The location of a proton is in the nucleus of an atom.
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6 0

3 years ago

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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.

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3 years ago

Determine the pH of a 2.8 ×10−4 M solution<br> of Ca(OH)2.

shepuryov [24]

Answer:

pH = 10.75

Explanation:

To solve this problem, we must find the molarity of [OH⁻]. With the molarity we can find the pOH = -log[OH⁻]

Using the equation:

pH = 14 - pOH

We can find the pH of the solution.

The molarity of Ca(OH)₂ is 2.8x10⁻⁴M, as there are 2 moles of OH⁻ in 1 mole of Ca(OH)₂, the molarity of [OH⁻] is 2*2.8x10⁻⁴M = 5.6x10⁻⁴M

pOH is

pOH = -log 5.6x10⁻⁴M

pOH = 3.25

pH = 14-pOH

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3 years ago

In the second step of this reaction, isocyanic acid reacts to form melamine and carbon dioxide: hnco(l)→c3n3(nh2)3(l)+co2(g) bal

slava [35]

Formula of isocyanic acid is HNCO. It colourless, volatile compound. It is poisonous inorganic compound. Melamine is synthesized from urea. The reaction involves two steps. In first step, urea gets converted to isocyanic acid which is an intermediate. In the second step, isocyanic acid gives melamine (molecular formula C₃H₆N₆) and carbon dioxide (CO₂). The balanced chemical reaction involved in second step is given below:

6 HNCO → 1 C₃N₃(NH₂)₃ + 3CO₂

The co-efficient of the reaction are: 6, 1, 3

7 0

4 years ago

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A chemist measures the energy change ΔH during the following reaction: C3H8 (g) +5O2 (g) →3CO2 (g) +4H2O (l) =ΔH−2220.kJ Use the

statuscvo [17]

Answer:

The reaction is exothermic.

Yes, released.

The heat released is 4,08x10³ kJ.

Explanation:

For the reaction:

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The ΔH is -2220 kJ, As ΔH is <0, <em>The reaction is exothermic.</em>

As the reaction is exothermic, the heat of the reaction will be <em>released.</em>

The heat released in 81,0g is:

81,0g C₃H₈× $\frac{1mol}{44,1g}$ × $\frac{2220kJ}{1mol}$ = <em>4,08x10³ kJ</em>

<em>-Using molar mass of C₃H₈ to convert mass to moles and knowing that there are released 2220 kJ per mole of C₃H₈-</em>

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3 years ago