Answer:
m = 3 moles/kg
Explanation:
This is a problem of freezing point depression, and the formula or expression to use is the following:
ΔT = i*Kf¨*m (1)
Where:
ΔT: Change of temperature of the solution
i: Van't Hoff factor
m: molality of solution
Kf: molal freezing point depression of water (Kf = 1.86 °C kg/mol)
Now, the value of i is the number of moles of particles obtained when 1 mol of a solute dissolves. In this case, we do not know what kind of solution is, so, we can assume this is a non electrolyte solute, and the value of i = 1.
Let's calculate the value m, which is the molality solving for (1):
m = ΔT/Kf (2)
Finally, let's calculate ΔT:
ΔT = T2 - T1
ΔT = 0 - (-5.58)
ΔT = 5.58 °C
Now, let's replace in (2):
m = 5.58/1.86
<em>m = 3 moles/kg</em>
<em>This is the molality of solution.</em>
<em>The other data of mass, can be used to calculate the molecular mass of this unknown solid, but it's not asked in the question.</em>
Answer:
<u>132.15</u>
Explanation:
Molar mass N = 14.00
Molar mass H = 1.01
Molar mass H4 = 1.01 x 4 = 4.04
Molar mass NH4 = 14.00 + 4.04 = 18.04
Molar mass (NH4)2 = 18.04 x 2 = 36.08
Molar mass S = 32.07
Molar mass O = 16.00
Molar mass O4 = 16.00 x 4 = 64.00
Molar mass SO4 = 32.07 + 64.00 = 96.07
Molar mass (NH4)2SO4 = 36.08 + 96.07 = <u>132.14</u>
Ans: 15.1 grams
Given reaction:
Na2CO3 + Ca(OH)2 → 2NaOH + CaCO3
Mass of Na2CO3 = 20.0 g
Molar mass of Na2CO3 = 105.985 g/mol
# moles of Na2CO3 = 20/105.985 = 0.1887 moles
Based on the reaction stoichiometry: 1 mole of Na2CO3 produces 2 moles of NaOH
# moles of NaOH produced = 0.1887*2 = 0.3774 moles
Molar mass of NaOH = 22.989 + 15.999 + 1.008 = 39.996 g/mol
Mass of NaOH produced = 0.3774*39.996 = 15.09 grams
Answer:
C is Correct
Explanation:
Protons and Neutrons make up the Nucleus while Electrons surround the nucleus in circular orbits with continuous rotation.
Apples turn brown when exposed to air because it undergoes aerial oxidation. Due to this, when the inside of the apple is exposed to the air containing oxygen and water, it turns brown. When apple is uncut, skin of the apple protects it from this process.
If the peeled apple in kept in the refrigerator, the oxidation reaction is greatly slowed down. This is because, rate of chemical reaction decreases with temperature. Hence, in refrigerator it would take several days for it to turn brown.
