10618 G of an Unknown Salt Is Dissolved in a Coffee

question 79

Multiple Choice

10.618 g of an unknown salt is dissolved in a coffee cup calorimeter that contains 50.0 mL of water. The measured temperature decreased from 23.8 °C to 22.7 °C. Identify the unknown salt. The specific heat of water is 4.184 J g^-1 °C^-1, and assume the density of the solution is 1.00 g mL^-1.

• A)NaF, Δ_rH = 0.91 kJ mol^-1
• B)NaBr, Δ_rH = -0.60 kJ mol^-1
• C)NaNO₃, Δ_rH = 20.50 kJ mol^-1
• D)LiNO₃, Δ_rH = -2.51 kJ mol^-1
• E)LiBr∙2H₂O, Δ_rH = -23.26 kJ mol^-1

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Definitions:

Subtractive Colour Mixing

A process involving the mixing of colored pigments where the combined colors absorb certain wavelengths of light and reflect others, creating a new color.

Complex Feature Detection

The ability of the brain to identify and process multifaceted aspects of sensory input for recognition and interpretation.

Inattentional Blindness

A psychological lack of attention that is not associated with any vision defects or deficits, making an individual fail to perceive an unexpected stimulus that is in plain sight.

Bottom-up Processing

A cognitive approach where perception starts with the smallest or simplest element and works up to the formation of a complete perception or understanding.