Question

magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas. the reactants in this reaction are
magnesium and magnesium chloride.
hydrochloric acid and hydrogen gas.
magnesium chloride and hydrogen gas.
magnesium and hydrochloric acid.
an irregular chunk of iron has a density of 7.87 g/cm3. a 14.5 gram chunk is added to a graduated cylinder. if the final volume of the graduated cylinder is 0.0394 l, what would be the starting volume?
1.84 ml
0.114 l
22.5 ml
37.6 ml

Explanation:

Step1: Identify reactants concept

Reactants are substances that start a chemical - reaction. Given magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas, the reactants are magnesium and hydrochloric acid.

Step2: Calculate volume of iron

Use the density formula $
ho=\frac{m}{V}$, where $
ho$ is density, $m$ is mass, and $V$ is volume. Rearranging for $V$, we get $V = \frac{m}{
ho}$. Given $m = 14.5$ g and $
ho=7.87$ g/cm³, then $V=\frac{14.5}{7.87}\text{ cm}^3\approx1.84$ cm³. Since 1 cm³ = 1 mL, the volume of iron is 1.84 mL.

Step3: Find starting volume of graduated - cylinder

The final volume of the graduated cylinder is $V_f = 0.0394$ L. Convert it to mL: $V_f=0.0394\times1000 = 39.4$ mL. Let the starting volume be $V_i$. We know $V_f=V_i + V_{iron}$. So $V_i=V_f - V_{iron}=39.4 - 1.84=37.6$ mL.

Answer:

1. D. magnesium and hydrochloric acid
2. D. 37.6 mL