An investigation is designed to examine the reaction rate between magnesium (\\text{Mg}) a… — ACT

An investigation is designed to examine the reaction rate between magnesium ( $\\text{Mg}$ ) and hydrochloric acid ( $\\text{HCl}$ ). In the baseline trial, a single $2.0\\text{ g}$ solid strip of $\\text{Mg}$ is placed into $100\\text{ mL}$ of $1.0\\text{ M}$ $\\text{HCl}$ solution at $22^\\circ\\text{C}$ , and the volume of hydrogen gas ( $\\text{H}_2$ ) released is recorded over $5\\text{ minutes}$ .

To isolate the effect of reactant surface area on the reaction rate, a second trial must be designed. Which of the following experimental setups would allow for a valid comparison to the baseline trial?

A
Reacting $4.0\\text{ g}$ of solid $\\text{Mg}$ strips with $100\\text{ mL}$ of $1.0\\text{ M}$ $\\text{HCl}$ at $22^\\circ\\text{C}$ , and recording the volume of $\\text{H}_2$ gas released over $5\\text{ minutes}$ .
Reacting $2.0\\text{ g}$ of ground $\\text{Mg}$ powder with $100\\text{ mL}$ of $1.0\\text{ M}$ $\\text{HCl}$ at $22^\\circ\\text{C}$ , and recording the volume of $\\text{H}_2$ gas released over $5\\text{ minutes}$ .Cevap
C
Reacting $2.0\\text{ g}$ of ground $\\text{Mg}$ powder with $200\\text{ mL}$ of $2.0\\text{ M}$ $\\text{HCl}$ at $30^\\circ\\text{C}$ , and recording the volume of $\\text{H}_2$ gas released over $5\\text{ minutes}$ .
D
Reacting a $2.0\\text{ g}$ solid strip of zinc ( $\\text{Zn}$ ) with $100\\text{ mL}$ of $1.0\\text{ M}$ $\\text{HCl}$ at $22^\\circ\\text{C}$ , and recording the volume of $\\text{H}_2$ gas released over $5\\text{ minutes}$ .

Cevap

Reacting

2.0\\text{ g}

of ground

\\text{Mg}

powder with

100\\text{ mL}

1.0\\text{ M}

\\text{HCl}

22^\circ\text{C}

over

5\text{ minutes}

is the correct modification because it increases the surface area of the magnesium while keeping the mass, concentration, volume, temperature, and duration constant.

The correct answer is the setup that reacts

2.0\\text{ g}

of ground

\\text{Mg}

powder with

100\\text{ mL}

1.0\\text{ M}

\\text{HCl}

22^\\circ\\text{C}

over

5\\text{ minutes}

. Grinding the metal strip into powder increases the total surface area exposed to the acid. Because the mass of magnesium, the volume and molarity of the acid, the temperature, and the trial duration are kept identical to the baseline trial, any difference in the reaction rate can be attributed solely to the increased surface area.

Adım Adım Çözüm

Determine the independent variable that needs to be altered and the control variables that must remain constant.

The independent variable to test is the surface area of the reactant. All other factors—reactant mass (

2.0\\text{ g}

), reactant type (

\\text{Mg}

), acid volume (

100\\text{ mL}

), acid concentration (

1.0\\text{ M}

), temperature (

22^\\circ\\text{C}

), and duration (

5\\text{ minutes}

)—must remain identical to the baseline trial.

To establish a causal relationship between surface area and reaction rate, only the surface area variable may differ between the trials.

Assess the options to find the setup that changes only the surface area of the magnesium.

Grinding the solid strip of magnesium into a powder increases its surface area. The option using

2.0\\text{ g}

of ground powder with the original acid concentration, volume, temperature, and time window successfully isolates this variable.

This configuration provides a valid experimental modification that conforms to scientific variable control.

Anahtar Kavram

Control of variables in follow-up experiments

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