Answer:
its the fourth one please mark as brainlest
Explanation:
Answer:
The answer to your question is 2.92 x 10⁻⁶ g
Explanation:
Data
mass of K = ?
atoms of K = 4.50 x 10¹⁶
Process
To answer this question just remember that the atomic mass of any element is equivalent to Avogadro's number.
1.- Look for the atomic number of Potassium
Atomic number = 39.10 g
2.- Use proportions and cross multiplication
39.10 g of K --------------- 6.023 x 10²³ atoms
x ----------------4.50 x 10¹⁶ atoms
x = (4.50 x 10¹⁶ x 39.10) / 6.023 x 10²³
-Simplify
x = 1.7595 x 10¹⁸ / 6.023 x 10²³
-Result
x = 2.92 x 10⁻⁶ g
You forgot to include the known characteristics of the solution.
I searched them and copy here:
volume: 1.000 liter
M = 0.0190 M
Now, you can start with the definition of mass percent.
mass percent = (grams of solute / grams of solution) * 100
grams of solute are obtained from the molar concentration:
M = (number of moles of solute) / (volume of solution in liters)
where number of moles = (grams) / (molar mass)
=> M = (grams of solute / molar mass of solute) / (volume of solution in liters)
=> grams of solute = M * (volume of solution in liters) * (molar mass of solute)
And density = (kg of solution / volume of solution in liters) =>
kg of solution = density * volume of solution in liters
grams of solution = density * (volume of solution in liters) * 1000 g/kg
=> mass percent = M * (volume of solution in liters) * (molar mass) / (density * volume of solution in liters * 1000 g/ kg) * 100
=> mass percent = M * molar mass * 10 / density
now replace the values known:
M = 0.0190 mol / liter
density = 1,000 kg / liter
molar mass of Ba(NO3)2 = 137.327 g/mol + 2*14.007 g/mol + 2*3*15.999 g/mol = 256.335 g/mol
=> mass percent = 0.0190 mol/liter * 256.335 g/mol * 10 kg/ g / (1.000 kg/liter)
=> mass percent = 48.7%
Answer:
278 ml of KOH.
Explanation:
The equation for the reaction is: Pb(NO3)2(aq) + 2KOH(aq) --> Pb(OH)2(s) + 2KNO3(aq)
Pb(NO3)2:
Half ionic equation:
Pb(NO3)2(aq) --> Pb2+ + 2NO3^-
Pb(OH)2 --> Pb2+ + 2OH-
Volume = 135 mL
Molar concentration = 0.775 M
Number of moles = molar concentration * volume
= 0.775 * 0.135
= 0.105 mol of Pb(NO3)2
Since 1 mole of Pb(NO3)2 reacted with 2 moles of KOH to give 1 mole of Pb2+ (Pb(OH)2).
By stoichiometry,
Number of moles of KOH = 0.105 * 2
= 0.21 mol
Molar concentration = number of moles/volume
Volume = 0.21/0.753
= 0.278 l
To ml, 0.278 l * 1000 ml/1l
= 278 ml of KOH.
