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Molecules of hydrogen chloride, HCl, and molecules of fluorine, F2, contain the same number of electrons. Hydrogen chloride boils at –85 °C and fluorine boils at –188 °C.Explain why there is a difference in the boiling points of HCl and F2.

F2 has van der Waals’ forces, whilst HCl has permanent dipole–dipole attractions. Permanent dipole–dipole attractions are much stronger than induced dipoles. More enegery is required to break the stronger pe...
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Answered by Ellis A. • Chemistry tutor
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Describe a typical cycle of a PCR reaction.

Polymerase Chain Reaction or PCR is the process of amplifying a sample of DNA. The first stage of a PCR cycle is known as the denaturation phase. This occurs at a temperature of 95C and lasts for approximate...
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Answered by Max B. • Biology tutor
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The theme of disguise is central to a number of Shakespeare’s plays. Write about any two characters (from different plays/sonnets) who employ some kind of disguise (physical or moral) and how this relates to wider issues of social identity.

“No plot device is more constantly recurrent in Shakespearean drama then is disguise,” writes critic P. Kreider.[1] Indeed, Shakespeare frequently uses cross-dressing as a means by which to spur a sequence o...
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Answered by Helena N. • English tutor
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Solve for x in the following equation using the quadratic formula, completing the square and factoring method: 2x^2-x-1=0

x=-1/2 and x=1
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Answered by Ravinder C. • Maths tutor
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How can I tell if the edition of my music score is reliable? - piano

"Urtext" (German for "original text") editions are generally the closest to the composer's intentions. Since centuries have passed, sometimes it is difficult to tell whether an Urtext edi...
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Answered by Luca S. • Music tutor
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