Question

18 multiple choice 1 point hydrochloric acid hcl is intense and can burn through materials as a component used in b is: \\( h_2 + cl_2 \longrightarrow 2hcl \\) how many molecules of hcl are produced from 0.35mol of \\( h_2 \\)? \\( 4.2 \times 10^{23} \\) molecules \\( 8.5 \times 10^{23} \\) molecules \\( 5.5 \times 10^{23} \\) molecules \\( 6.4 \times 10^{23} \\) molecules 19 multiple choice 1 point \\( bacl_2 (aq) + na_2so_4 (aq) \longrightarrow baso_4 (s) + 2nacl (aq) \\) this is an example of a \\( \underline{quadquad} \\) reaction. double replacement combination single replacement decomposition

Explanation:

Question 18 (Subfield: Chemistry)

Step1: Determine mole ratio

From the reaction $\ce{H_{2} + Cl_{2} -> 2HCl}$, the mole ratio of $\ce{H_{2}}$ to $\ce{HCl}$ is $1:2$. So moles of $\ce{HCl}$ = $2\times$ moles of $\ce{H_{2}}$.
Moles of $\ce{HCl}$ = $2\times0.35\ \text{mol} = 0.7\ \text{mol}$.

Step2: Use Avogadro's number

Avogadro's number is $6.022\times 10^{23}\ \text{molecules/mol}$. Number of molecules = moles $\times$ Avogadro's number.
Number of $\ce{HCl}$ molecules = $0.7\ \text{mol}\times6.022\times 10^{23}\ \text{molecules/mol} \approx 4.2\times 10^{23}\ \text{molecules}$.

In the reaction $\ce{BaCl_{2}(aq) + Na_{2}SO_{4}(aq) -> BaSO_{4}(s) + 2NaCl(aq)}$, the cations ($\ce{Ba^{2+}}$ and $\ce{Na^{+}}$) and anions ($\ce{Cl^{-}}$ and $\ce{SO_{4}^{2-}}$) exchange partners. This matches the definition of a double replacement reaction (ions swap to form new compounds, often a precipitate, gas, or water). Combination reactions form a single product, single replacement has one element replacing another, and decomposition breaks a compound into simpler parts—none of these fit here.

Answer:

$4.2\times 10^{23}$ molecules (corresponding to the first option)

Question 19 (Subfield: Chemistry)