Question

experiment #4 predict the mass of oxygen that will be left over after the reaction of 48.6 grams of magnesium with 50.0 grams of oxygen. magnesium + oxygen -----> magnesium oxide + oxygen 48.6 g + 50.0 g -----> 80.6 g + g o₂ leftover practice problems if 50 grams of sodium reacts with chlorine to form 126 grams of salt. how many grams of chlorine reacted? 50g na + cl → 126 g nacl 2. if 20 grams of aluminum reacts with 200 grams of bromide to form aluminum bromide, and no aluminum is left after the reaction, but 23 grams of bromine remain unreacted. how many grams of aluminum bromide were formed? 20g al + 200g br → g albr₃ + 23g br(remain)

Explanation:

Step1: Use law of conservation of mass for first problem

The law of conservation of mass states that the total mass of reactants equals the total mass of products. Let the mass of leftover oxygen be $x$. So, $48.6 + 50.0=80.6 + x$.

Step2: Solve for $x$

$x=(48.6 + 50.0)-80.6$
$x = 18.0$ grams

Step3: Use law of conservation of mass for second problem

Let the mass of chlorine be $y$. Then $50 + y=126$, so $y = 126 - 50=76$ grams

Step4: Use law of conservation of mass for third problem

Let the mass of aluminum bromide be $z$. The mass of reactants is $20+200$ grams and the mass of un - reacted bromine is 23 grams. So, $20+200=z + 23$.

Step5: Solve for $z$

$z=(20 + 200)-23$
$z = 197$ grams

Answer:

1. 18.0 grams
2. 76 grams
3. 197 grams