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Serga [27]
3 years ago
5

Determine the molality of an aqueous solution that is 15.5 percent urea by mass.

Chemistry
1 answer:
DaniilM [7]3 years ago
3 0

15.5% by mass is equivalent 15.5 g urea in 100 g solution or 155 g urea in 1 kg solution. <span>

<span>we know that molality = moles solute / kg solvent

<span>moles solute = 155 g / 60 g/mol = 2.58 moles urea

</span></span></span>

Since there are 155 g urea in 1000g solution, hence the solvent is 845 g or 0.845 kg

So:<span>
<span>molality = 2.58 / 0.845 = 3.06 m</span></span>

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Write the isotope notation for an element with 42 protons and 96 neutrons.
tankabanditka [31]

Answer:138

Explanation:

4 0
3 years ago
Read 2 more answers
PLEASE HELP ME!!! ASAP
shtirl [24]

Answer:

Theoretical yield of the reaction = 34 g

Excess reactant is hydrogen

Limiting reactant is nitrogen

Explanation:

Given there is 100 g of nitrogen and 100 g of hydrogen

Number of moles of nitrogen = 100 ÷ 28 = 3·57

Number of moles of hydrogen = 100 ÷ 2 = 50

Reaction between nitrogen and hydrogen yields ammonia according to the following chemical equation

N2 + 3H2 → 2NH3

From the above chemical equation for every mole of nitrogen that reacts, 3 moles of hydrogen will be required and 2 moles of ammonia will be formed

Now we have 3·57 moles of nitrogen and therefore we require 3 × 3·57 moles of hydrogen

⇒ We require 10·71 moles of hydrogen

But we have 50 moles of hydrogen

∴ Limiting reactant is nitrogen and excess reactant is hydrogen

From the balanced chemical equation the yield will be 2 × 3·57 moles of ammonia

Molecular weight of ammonia = 17 g

∴ Theoretical yield of the reaction = 2 × 3·57 × 17 = 121·38 g

5 0
3 years ago
Suppose you will fill a glass with ice cubes. When the ice cubes melt, is the glass still full
goblinko [34]
No. It will not still be full. The reason being is because when it melts, it's almost the same thing as compacting things down into another object (container). Therefore, you will have some room left i the glass. Like, if your trashcan was over-flowing, and you push it down to compact it so you can add more trash. So when the ice melts, it will not be full.
7 0
3 years ago
Ideal He gas expanded at constant pressure of 3 atm until its volume was increased from 9 liters to 15 liters. During this proce
kkurt [141]

Explanation:

The given data is as follows.

             P = 3 atm

                = 3 atm \times \frac{1.01325 \times 10^{5} Pa}{1 atm}  

                 = 3.03975 \times 10^{5} Pa

    V_{1} = 9 L = 9 \times 10^{-3} m^{3}    (as 1 L = 0.001 m^{3}),  

        V_{2} = 15 L = 15 \times 10^{-3} m^{3}

            Heat energy = 800 J

As relation between work, pressure and change in volume is as follows.

                  W = P \times \Delta V

or,                W = P \times (V_{2} - V_{1})

Therefore, putting the given values into the above formula as follows.

                  W = P \times (V_{2} - V_{1})

                      = 3.03975 \times 10^{5} Pa \times (15 \times 10^{-3} m^{3} - 9 \times 10^{-3} m^{3})

                      = 1823.85 Nm

or,                   = 1823.85 J

As internal energy of the gas \Delta E is as follows.

                     \Delta E = Q - W

                                  = 800 J - 1823.85 J

                                  = -1023.85 J

Thus, we can conclude that the internal energy change of the given gas is -1023.85 J.

8 0
3 years ago
For the reaction A (g) → 2 B (g), K = 14.7 at 298 K. What is the value of Q for this reaction at 298 K when ∆G = -20.5 kJ/mol?
harina [27]

Answer:

Q= 245 =2.5 * 10^2

Explanation:

ΔG = ΔGº + RTLnQ, so also ΔGº= - RTLnK

R= 8,314 J/molK, T=298K

ΔGº= - RTLnK = - 6659.3 J/mol = - 6.7 KJ/mol

ΔG = ΔGº + RTLnQ → -20.5KJ/mol = - 6.7 KJ/mol + 2.5KJ/mol* LnQ

→ 5.5 = LnQ → Q= 245 =2.5 * 10^2

6 0
4 years ago
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