Question

I have 5 chemistry questions here.

The Ideal Gas Equation states:

PV = nRT

where "P" equals the pressure of the gas, "V" equals the volume of the container, "n" equals the number of moles of gas in the container, R = the Gas constant (0.082057 L atm K^–1 mol^–1), and "T" equals the temperature of the gas

1. Calculate the volume (in litres) of a sealed container with 5.67 mol of an ideal gas at a temperature of 374.7 K and pressure of 11.15 atm.

2. The temperature is increased by 67.4 K.

Calculate the new pressure of the system (assuming no change in volume).

3. A chocolate bar was found to have 3.5609 kilojoules of chemical energy.

Calculate the number of joules of chemical energy in the chocolate bar.

4. Calculate the number of calories in this chocolate bar.

1.0000 joule = 0.2390 calories

5.

The pH of a solution is found by the following equation:

pH = –log₁₀[H⁺]

Calculate the pH of a solution with a [H+] of 0.0218 mol L^–1.

Answer 1

The ideal gas equation is PV = nRT.

1) Given data: n =5.67 mol, T = 374.7 K, P = 11.15 atm. R = 0.082057 L atm K^-1 mol^-1 and V =?

Using Ideal gass equation, PV = nRT,

V = nRT / PV

= 5.67 X 374.7 X 0.082057 / 11.15

V = 15.64 L.

2) PV = nRT

Implies, P = (nR/V) x T

so, P = K x T ..................(constant K = nR/V)

P/T = K

so P1/T1 = K and P2/T2 = K

so, P2/T2= P1/T1

So, P2 = (P1/T1) x T2.............(I)

We have P1 = 11.15 atm, T1 = 374.7 K and new increased Temperature T2 = T1 + 67.4 = 374.7 + 67.4 = 442.1 K

put all these values in above eq. I

P2 = (11.15/ 374.7) x 442.1

=13.16 atm

The as temperature increased by 67.4 K the pressure is increased to 13.16 atm i.e. increased by 2.01 atm.

Hence the new pressure of the system is 13.16 atm.

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3) Let E be the energy in chocolate bar and given that,

E = 3.5609 kJ

so, E = 3.5609 x 1000 J ...........(since, 1kJ = 1000 J)

so, E = 3560.9 J.

Hence number of Joules in chocolate bar are 3560.9

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4) E = 3560.9 J

so, E = 3560.9 x 0.2390 calories ...........(since, 1 J = 0.2390 calories)

so, E = 851.06 calories.

Hence number of calories in chocolate are 851.06.

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5) Given that, [H⁺] = 0.0218 mol/L

Formula, pH = -log₁₀[H⁺]

so, pH = -log₁₀[0.0218]

pH = 1.6615

Hence the pH of given solution is 1.6615.

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