A Quantity of 7

question 164

Multiple Choice

A quantity of 7.85 g of a compound having the empirical formula C₅H₄ is dissolved in 301 g of benzene. The freezing point is 1.05 ° C below that of pure benzene (k_f = 5.12 ° C/m) . The molar mass of the species in solution in benzene is:

• A) 64.0 g/mol
• B) 38.3 g/mol
• C) 11.5 g/mol
• D) 127 g/mol
• E) 194 g/mol

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Definitions:

Pretest-Posttest

A research design that measures the effect of an intervention by comparing conditions before and after the intervention is applied.

Posttest-Only

A research design where measures are taken only after the experimental manipulation, without a pretest comparison.

Mortality

The loss of subjects who decide to leave an experiment. Mortality is a threat to internal validity when the mortality rate is related to the nature of the experimental manipulation.

Experimental Design

A research design used to test hypotheses and establish cause-effect relationships by manipulating one or more independent variables and observing the effect on dependent variables.