Question

8 multiple choice 1 point
a solution of nickel sulfide (nis) with a mass of 8.5g was created using 4.4g of nickel and excess of sulfur. calculate the theoretical yield of nis.
$s + ni \
ightarrow nis$
\\(\circ\\) 8.6g nis
\\(\circ\\) 7.9g nis
\\(\circ\\) 6.8g nis
\\(\circ\\) 8.4g nis

9 multiple choice 1 point
when a reaction produces a single product, a \\(\\_\\_\\_\\_\\_\\_\\) reaction has occurred.
\\(\circ\\) decomposition
\\(\circ\\) double replacement
\\(\circ\\) combination
\\(\circ\\) single replacement

Explanation:

Question 8

Step1: Find molar mass of Ni and NiS

Molar mass of Ni: $58.69\ \text{g/mol}$. Molar mass of NiS: $58.69 + 32.07 = 90.76\ \text{g/mol}$.

Step2: Moles of Ni

Moles of Ni = $\frac{\text{mass of Ni}}{\text{molar mass of Ni}} = \frac{4.4\ \text{g}}{58.69\ \text{g/mol}} \approx 0.075\ \text{mol}$.

Step3: Moles of NiS (1:1 ratio)

From reaction $S + Ni
ightarrow NiS$, moles of NiS = moles of Ni = $0.075\ \text{mol}$.

Step4: Theoretical yield of NiS

Mass of NiS = moles × molar mass = $0.075\ \text{mol} × 90.76\ \text{g/mol} \approx 6.8\ \text{g}$? Wait, no, wait: Wait, 4.4g Ni: 4.4 / 58.69 ≈ 0.075 mol. Then NiS mass: 0.075 90.76 ≈ 6.8g? Wait, but let's recalculate: 58.69 + 32.07 = 90.76. 4.4 / 58.69 = 0.075. 0.075 90.76 = 6.807g ≈ 6.8g. Wait, but let's check again. Wait, 4.4g Ni: moles = 4.4 / 58.69 ≈ 0.075 mol. Then NiS is 1:1, so mass is 0.075 * 90.76 ≈ 6.8g. So the answer is 6.8g NiS.

A combination reaction (also called synthesis) is when two or more reactants combine to form a single product (e.g., $A + B
ightarrow AB$). Decomposition is opposite (one reactant → multiple products). Double replacement involves two compounds exchanging ions (two products). Single replacement is one element replacing another in a compound (two products). So the reaction with a single product is combination.

Answer:

6.8g NiS (Option: 6.8g NiS)

Question 9