# Tutor profile: Steffy R.

## Questions

### Subject: Pre-Calculus

Find the vertex of the parabola y=2x^2-8x+7.

We have that x= -{b}/{2a}= -(-8)/(2*2)=2, and then y = 2(2^2)-8(2)+7 y = 8-16+7 y = -1

### Subject: Chemistry

What is the bond dissociation enthalpy of an oxygen-to-oxygen double bond if the enthalpy of combustion for one mole of ethane gas (C2H6) is approximately –1.911 x 103 kJ?

C2H6 + (7/2)O2 -> 2CO2 + 3H2O deltaH= Sum of dissociation energies of bone broken - Sum of dissociation energies of bonds created deltaH (Combustion) = (C-C) + 6*(C-H)+ (7/2)*(O=O) - 4*(C=O) + 6*(O-H) -1911 = 348+ 6*413 + (7/2)*(O=O) - 4*799 -6*463 -1911 -348-2478+3196+2778= (7/2)*(O=O) (1237*2)/7 = (O=O) (O=O) = 353.4 KJ/moles

### Subject: Algebra

5(- 3x - 2) - (x - 3) = -4(4x + 5) + 13

5 (- 3 x - 2) - (x - 3) = - 4 (4 x + 5) + 13 -15 x - 10 - x + 3 = - 16 x - 20 + 13 - 16 x - 7 = - 16 x - 7 0 = 0

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