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Questions in chemistry

[Done] Which example involves a phase change in which heat energy is released by the substance? A. freezing ice cream B. cooking a pot of soup C. melting ice under sunlight D. watching frost disappear into air

[Done] Given: [tex]$2 LiBr+Ba \rightarrow BaBr_2+2 Li$[/tex] In this chemical reaction, 325 grams of barium (Ba) react completely. How many moles of lithium (Li) are produced? A. 1.18 mol B. 2.37 mol C. 4.73 mol D. [tex]$16.4 mol^{\prime}$[/tex] E. 32.9 mol

[Done] What is the pH of [tex]$5.22 \times 10^{-3} M HClO _4( H ^{+})$[/tex] solution? A. none of these B. 5.22 C. [tex]$1.92 \times 10^{-12}$[/tex] D. 0.438 E. 2.28

[Done] What is the value for [tex]$\Delta G$[/tex] at 100 K if [tex]$\Delta H=27 kJ / mol$[/tex] and [tex]$\Delta S$ =0.09 kJ /( mol \cdot K )$[/tex] ? A. [tex]$\Delta G=2700 kJ / mol$[/tex] B. [tex]$\Delta G=-36 kJ / mol$[/tex] C. [tex]$\Delta G=18 kJ / mol$[/tex] D. [tex]$\Delta G=0 kJ / mol$[/tex]

[Done] What is $K_b$ for $C_5H_5N(aq) + H_2O(l) = C_5H_5NH^+(aq) + OH^-(aq)$? A. $K_b = \frac{[C_5H_5N]}{[C_5H_5NH^+][OH^-]}$ B. $K_b = \frac{[C_5H_5NH^+ HOH^-]}{[C_5H_5N]}$ C. $K_b = \frac{[C_5H_5NH^+]}{[C_5H_5N]}$ D. $K_b = [C_5H_5N^+] |O^-|$

[Done] A beaker contains a solution of calcium hydroxide $\left( Ca ( OH )_2\right)$ in water. A student places a straw in the beaker and then breathes into the solution through the straw. As the student breathes into the solution, a white precipitate forms. What is the most likely composition of the precipitate? A. $H _2 O$ B. $CaCO _3$ C. $CH _3 OH$

[Done] What is the pH of $9.55 \times 10^{-7} M HCl \left( H ^{+}\right)$ solution? A. 9.55 B. 0.166 C. $1.05 \times 10^{-8}$ D. 6.02 E. none of these available choices

[Done] Which of the following polymers need at least one diene monomer for their preparation? A) Dacron B) Neoprene C) Buna-S D) Both B and C

[Done] Sodium $(Na)$ has 11 protons and 12 neutrons. What is its isotope notation? A. $Na -11$ B. $Na-12$ C. $Na -23$ D. $Na -34$

[Done] Select the correct answer from each drop-down menu. Determine the molecular formula of the compound. A compound is used as a gasoline additive. It has a molecular weight of 60.10 atomic mass units and an empirical formula of [tex]$C _3 H _8 O$[/tex]. The molecular formula is C