<p>Magnesium sulfate is often used in first-aid hot packs, giving offheat when dissolved in water. When 2.00g of MgS)4 dissolves in 15.0mL of water at 25C in a coffee-cup calorimeter, 1.51 kJ of heat is evolved.</p>

<p>What is the final temperature of the solution? (Specific heat of water is 4.18 J/g*C).</p>

<p>I was given two equations from the book in this chapter:</p>

<p>Heat flow equations (q=m<em>c</em>change in temp)

Coffee-cup calorimeter (q= -m of water * 4.18J/g * C * Change in t)</p>

<p>I used the Coffee-cup equation. but apparently I was wrong.</p>

<p>This is what I did.</p>

<p>1.51= -15g * 4.18J/gC * (tF - 25C)</p>

<p>but the answer book shows it as this</p>

<p>1.51= 15g * 4.18J/gC * (tF - 25C)</p>

<p>Why do you use the Heat flow equation instead of Coffee cup calorimeter equation for this problem?</p>