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Questions in chemistry

📝 Answered - A cube of iron $\left(C_p=0.450 J / g \cdot{ }^{\circ} C \right)$ with a mass of 55.8 g is heated from $25.0^{\circ} C$ to $49.0^{\circ} C$. How much heat is required for this process? Round your answer to three significant figures. Use the formula $q=m C_y \Delta T$.

📝 Answered - Rolf prepares four solutions using different solutes as shown in the table below. | Solution | Preparation | Solubility of the solutes | |---|---|---| | A | Rolf added 20 g of solute to 100 g of water and mixed the solution. | The solute in solution A has a solubility of [tex]$37 g / 100 g H _2 O$[/tex] at [tex]$20^{\circ} C$[/tex]. | | B | Rolf added 10 g of solute to 100 g of water and mixed the solution. | The solute in solution B has a solubility of [tex]$10 g / 100 g H _2 O$[/tex] at [tex]$20^{\circ} C$[/tex]. | | C | Rolf added 65 g of solute to 100 g of water, mixed the solution, and then heated the solution. | The solute in solution C has a solubility of [tex]$32 g / 100 g H _2 O$[/tex] at [tex]$20^{\circ} C$[/tex]. | | D | Rolf added 7 g of solute to 100 g of water, mixed the solution, and then heated the solution. | The solute in solution D has a solubility of [tex]$4 g / 10 A H _2 O$[/tex] at [tex]$20^{\circ} C$[/tex]. | Which solution is unsaturated? A. Solution A B. Solution B C. Solution C D. Solution D

📝 Answered - A sample of an unknown substance has a mass of 0.158 kg. If [tex]$2,510.0 J$[/tex] of heat is required to heat the substance from [tex]$32.0^{\circ} C$[/tex] to [tex]$61.0^{\circ} C$[/tex], what is the specific heat of the substance? Use [tex]$q=m C_p \Delta T$[/tex]. A. [tex]$0.171 J /\left( g _{ i }{ }^{\circ} C \right)$[/tex] B. [tex]$0.548 J /\left( g _{ i }{ }^{\circ} C \right)$[/tex] C. [tex]$15.9 J /\left( g _{ i }{ }^{\circ} C \right)$[/tex] D. [tex]$86.6 J /\left( g _{ i }{ }^{\circ} C \right)$[/tex]

📝 Answered - Give 5 environmental impacts of mining.

📝 Answered - Which equation shows how to calculate how many grams $(g)$ of KCl would be produced from 4 mol KOH? The balanced reaction is: $MgCl_2+2 KOH \rightarrow Mg(OH)_2+2 KCl$ A. $\frac{4 mol KOH }{1} \times \frac{1 mol KCl }{2 mol KOH } \times \frac{74.55 g KCl }{1 mol KCl }$ B. $\frac{4 mol KOH }{1} \times \frac{2 mol KCl }{1 mol KOH } \times \frac{74.55 g KCl }{1 mol KCl }$ C. $\frac{4 mol KOH }{1} \times \frac{2 mol KCl }{2 mol KOH } \times \frac{74.55 g KCl }{1 mol KCl }$ D. $\frac{4 mol KOH }{1} \times \frac{1 mol KOH }{1 mol KCl } \times \frac{74.55 g KCl }{1 mol KCl }$

📝 Answered - Consider the following intermediate chemical equations: [tex] \begin{array}{ll} P_4(s)+6 Cl_2(g) \rightarrow 4 PCl_3(g) & \Delta H_1=-2,439 kJ \\ 4 PCl_5(g) \rightarrow P_4(s)+10 Cl_2(g) & \Delta H_2=3,438 kJ \end{array} [/tex] What is the enthalpy of the overall chemical reaction [tex]PCl _5(g) \rightarrow PCl _3(g)+ Cl _2(g)[/tex]? A. -999 kJ B. -250 kJ C. 250 kJ D. 999 kJ

📝 Answered - The preparations of two aqueous solutions are described in the table below. For each solution, write the chemical formulas of the major species present at equilibrium. You can leave out water itself. Write the chemical formulas of the species that will act as acids in the 'acids' row, the formulas of the species that will act as bases in the 'bases' row, and the formulas of the species that will act as neither acids nor bases in the 'other' row. You will find it useful to keep in mind that [tex]$NH _3$[/tex] is a weak base. | 0.9 mol of HBr is added to 1.0 L of a [tex]$0.9 M NH _3$[/tex] solution. | acids: $\square$ bases: $\square$ other: $\square$ | | 0.41 mol of KOH is added to 1.0 L of a solution that is 1.5 M in both [tex]$NH _3$[/tex] and [tex]$NH _4 Br$[/tex]. | acids: $\square$ bases: $\square$ other: $\square$ |

📝 Answered - A sample of tin ($Cp = 0.227 J / g \cdot{ }^{\circ} C$) is placed in a freezer. Its temperature decreases from $15.0^{\circ} C$ to $-10.0^{\circ} C$ as it releases 543 J of energy. What is the mass of the sample? Round your answer to three significant figures. Use the formula $q=m C_y \Delta T$. $\square$ g

📝 Answered - An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?

📝 Answered - Draw the Lewis structure for the hypochlorite ion, [tex]$ClO^{-}$[/tex]. Include lone pairs and formal charges.