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2 years ago

How many atoms of gold (Au,196.97 g/mol) are in a gold nugget with a mass of 4.259?

Chemistry

1 answer:

AveGali [126]2 years ago

5 0

Mass of gold nugget = 4.259 g

Calculating the moles of gold from mass and molar mass:

$4.259 g Au * \frac{1 mol Au}{196.97 g Au} = 0.0216 mol Au$

Calculating the atoms of Au:

$0.0216 mol Au * \frac{6.022 * 10^{23} atoms Au}{1 mol Au} = 1.3*10^{22} atoms Au$

Therefore, $1.3 * 10^{22} atoms Au$ are present in a gold nugget with a mass of 4.259 g.

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BH+ClO4- is a salt formed from the base B (Kb = 1.00e-4) and perchloric acid. It dissociates into BH+, a weak acid, and ClO4-, w

Len [333]

Answer:

The pH of 0.1 M BH⁺ClO₄⁻ solution is 5.44

Explanation:

Given: The base dissociation constant: $K_{b}$ = 1 × 10⁻⁴, Concentration of salt: BH⁺ClO₄⁻ = 0.1 M

Also, water dissociation constant: $K_{w}$ = 1 × 10⁻¹⁴

The acid dissociation constant ( $K_{a}$ ) for the weak acid (BH⁺) can be calculated by the equation:

$K_{a}. K_{b} = K_{w}$

$\Rightarrow K_{a} = \frac{K_{w}}{K_{b}}$

$\Rightarrow K_{a} = \frac{1\times 10^{-14}}{1\times 10^{-4}} = 1\times 10^{-10}$

Now, the acid dissociation reaction for the weak acid (BH⁺) and the initial concentration and concentration at equilibrium is given as:

Reaction involved: BH⁺ + H₂O ⇌ B + H₃O+

Initial: 0.1 M x x

Change: -x +x +x

Equilibrium: 0.1 - x x x

The acid dissociation constant: $K_{a} = \frac{\left [B \right ] \left [H_{3}O^{+}\right ]}{\left [BH^{+} \right ]} = \frac{(x)(x)}{(0.1 - x)} = \frac{x^{2}}{0.1 - x}$

$\Rightarrow K_{a} = \frac{x^{2}}{0.1 - x}$

$\Rightarrow 1\times 10^{-10} = \frac{x^{2}}{0.1 - x}$

$As, x$

$\Rightarrow 0.1 - x = 0.1$

$\therefore 1\times 10^{-10} = \frac{x^{2}}{0.1 }$

$\Rightarrow x^{2} = (1\times 10^{-10})\times 0.1 = 1\times 10^{-11}$

$\Rightarrow x = \sqrt{1\times 10^{-11}} = 3.16 \times 10^{-6}$

Therefore, the concentration of hydrogen ion: x = 3.6 × 10⁻⁶ M

Now, pH = - ㏒ [H⁺] = - ㏒ (3.6 × 10⁻⁶ M) = 5.44

Therefore, the pH of 0.1 M BH⁺ClO₄⁻ solution is 5.44

5 0

2 years ago

The standard cell potential (E°cell) for the reaction below is +0.63 V. The cell potential for this reaction is ________ V when

tia_tia [17]

Answer : The cell potential for this reaction is 0.50 V

Explanation :

The given cell reactions is:

$Pb^{2+}(aq)+Zn(s)\rightarrow Zn^{2+}(aq)+Pb(s)$

The half-cell reactions are:

Oxidation half reaction (anode): $Zn\rightarrow Zn^{2+}+2e^-$

Reduction half reaction (cathode): $Pb^{2+}+2e^-\rightarrow Pb$

First we have to calculate the cell potential for this reaction.

Using Nernest equation :

$E_{cell}=E^o_{cell}-\frac{2.303RT}{nF}\log \frac{[Zn^{2+}]}{[Pb^{2+}]}$

where,

F = Faraday constant = 96500 C

R = gas constant = 8.314 J/mol.K

T = room temperature = $25^oC=273+25=298K$

n = number of electrons in oxidation-reduction reaction = 2

$E^o_{cell}$ = standard electrode potential of the cell = +0.63 V

$E_{cell}$ = cell potential for the reaction = ?

$[Zn^{2+}]$ = 3.5 M

$[Pb^{2+}]$ = $2.0\times 10^{-4}M$

Now put all the given values in the above equation, we get:

$E_{cell}=(+0.63)-\frac{2.303\times (8.314)\times (298)}{2\times 96500}\log \frac{3.5}{2.0\times 10^{-4}}$

$E_{cell}=0.50V$

Therefore, the cell potential for this reaction is 0.50 V

5 0

3 years ago

Need help with balancing equations!

shusha [124]

Answer:

Fe2O3 + 3CO → 2Fe + 3CO2

Explanation:

the numbers in front are the numbers you need

4 0

2 years ago

Read 2 more answers

What is a good essential question for the subject molecular compounds

Mashutka [201]

Why do molecules combined into chains?

6 0

3 years ago

A. how do you determine the charge of an element?

NemiM [27]

Answer:

Explanation:

A. The charge on an element is determined by the differences between the number of protons and electrons in an atom.

An atom will have no charges if the number of protons and electrons are the same.

When an atom loses or gains electrons, the number of electrons will either decrease or increase
if the number of electrons is more than the number of protons, the excess electrons is the charge on the atom. And this makes the atom become a negatively charged ion.
if the number of electrons is lesser than the number of protons, the deficient electrons makes the atom a positively charged ion. The number of electrons by which the atom is deficient makes the atom a positively charged ion.

Charge = number of protons - number of electrons

B. Electrons form the charges they do because with the charge, they become stable like the noble gases.

The desire of every atom is to have stable electronic configuration like those of the noble gases.

A potassium atom with a configuration 2 8 8 1 will prefer to lose an electron to become an Argon atom making the ion stable.

3 0

2 years ago