In a Chemical Reaction, the Rate at Which the Amount $\frac { \mathrm { dy } } { \mathrm { dt } } = - 0.7 \mathrm { y }$

question 55

Multiple Choice

In a chemical reaction, the rate at which the amount of a reactant changes with time is proportional to the amount present, such that $\frac { \mathrm { dy } } { \mathrm { dt } } = - 0.7 \mathrm { y }$ , when $\mathrm { t }$ is measured in hours. If there are $63 \mathrm {~g}$ of reactant present when $t$ $= 0$ , how many grams will be left after 2 hours? Give your answer to the nearest tenth of a gram.

• A) 15.5 g
• B) 23.3 g
• C) 0.2 g
• D) 7.8 g

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