Which of the following elements is most likely to react?<br> A.Cu<br> B.Al<br> C.Li<br> D.Mg

We get the pressure of the hydrogen gas from the difference between the measured pressure and the vapor pressure of water:
total pressure = Pressure of H2 + Vapor Pressure of H2O
1.00 atm = Pressure of H2 + 0.0313 atm
Pressure of H2 = 1.00 atm - 0.0313 atm = 0.9687 atm

From the ideal gas law,
PV = nRT
we can calculate for the number of moles of H2 as
n = PV/RT = (0.9687 atm)(0.246L) / (0.08206 L·atm/mol·K)(298.15 K)
= 0.00974 mol H2
where
V = 246 mL (1 L / 1000 mL) = 0.246 L
T = 25 degrees Celsius + 273.15 = 298.15 K

We use the mole ratio of Na and H2 from the reaction of sodium metal with water as shown in the equation
2Na(s) + 2H2O(l) → 2 NaOH(aq) + H2(g)
and the molar mass of sodium Na to get the mass of sodium used in the reaction:
mass of Na = 0.00974 mol H2 (2 mol Na /1 mol H2)(22.99 g Na/1 mol Na)
= 0.448 grams of sodium

4 0

3 years ago

For the galvanic (voltaic) cell Fe(s) + Mn2+(aq) → Fe2+(aq) + Mn(s) (E°= 0.77 V at 25°C), what is [Fe2+] if [Mn2+] = 0.040 M and

avanturin [10]

Answer:

0.01836 M

Explanation:

Again the reaction equation is;

Fe(s) + Mn2+(aq) → Fe2+(aq) + Mn(s)

E°cell= 0.77 V

Ecell= 0.78 V

[Mn2+] = 0.040 M

[Fe2+] = the unknown

n=2

From Nernst's equation;

Ecell= E°cell- 0.0592/n log Q

0.78= 0.77 - 0.0592/2 log [Fe2+] /[0.040]

0.78-0.77= - 0.0592/2 log [Fe2+] /[0.040]

0.01/ -0.0296= log [Fe2+] /[0.040]

-0.3378= log [Fe2+] /[0.040]

Antilog(-0.3378) = [Fe2+] /[0.040]

0.459= [Fe2+] /[0.040]

[Fe2+] = 0.459 × 0.040

[Fe2+] = 0.01836 M

7 0

4 years ago

A 0.3146 g sample of a mixture of NaCl ( s ) and KBr ( s ) was dissolved in water. The resulting solution required 45.70 mL of 0

Masteriza [31]

Answer:

The answer to the question is

The mass percentage of NaCl(s) in the mixture is 49.7%

Explanation:

The given variables are

mass of sample of mixture = 0.3146 g

Volume of AgNO₃ required to react comletely with the chloride ions = 45.70 mL

Concentration of the AgNO₃ added = 0.08765 M

The equations for the reactions oare

NaCl(aq) + AgNO₃ (aq) = AgCl(s) + NaNO₃(aq)

AgNO₃ (aq) + KBr (aq) → AgBr (s) + KNO₃

The equation for the reaction shows one mole of NaCl reacts with one mole of AgNO₃ to form one mole of AgCl

Thus 45.70 mL of 0.08765 M solution of AgNO₃ contains $\frac{45.7}{1000} (0.08765) = 0.004 moles$

Therefore the sum of the number of moles of Br⁻ and Cl⁻

precipitated out of the solution = 0.004 moles

Thus if the mass of NaCl in the sample = z then the mass of KBr = y

However the mass of the sample is given as 0.3146 g which means the molarity of the solution is 0.004 moles

given by

$\frac{z}{58.44} + \frac{y}{119} = 0.004 moles$ and z + y = 0.3146

Therefore z = 0.3146 - y which gives

$\frac{(0.3146-y)}{58.44} + \frac{y}{119} = 0.004 moles$

-8.7×10⁻³y +0.54×10⁻³ = 0.004

or 8.7×10⁻³y = 1.37769× 10⁻³

y = 0.158 g and z = 0.156 Thus the mass of NaCl = 0.156 g and the mass percentage = 0.156/0.3146×100 = 49.7% NaCl

The mass percentage of NaCl(s) in the mixture is 49.7%

8 0

3 years ago

Which of the following elements is most likely to react? A.Cu B.Al C.Li D.Mg