Blog

An unknown substance has a mass of 23.8 g. The temperature of the substance increases from 27.1oC to 42.7oC when 89.1 J of heat is added to the substance. Substance Specific Heat (J/g·°C) Lead 0.130 Silver 0.240 Copper 0.385 Iron 0.442 Aluminum 0.892 Water 4.184   a) What is the specific heat of the unknown substance ? [a] J/goC b) Based on the substances shown on the table above, what is the most likely identity of the unknown substance ?[b]

Consider the reaction: 4HCl(aq) + MnO2(s) → MnCl2(aq) + 2H2O(l) + Cl2(g) A sample of 29.3 g MnO2 (molar mass = 86.94 g/mol) is added to a solution containing 37.0 g HCl (molar mass = 36.46 g/mol). a) How many moles of Cl2 can be obtained from MnO2? b) How many moles of Cl2 can be obtained from HCl? c) How many moles of Cl2 can be obtained in this reaction? d) How many grams of Cl2 (molar mass = 70.91 g/mol) can be obtained in this reaction? e) What is the limiting reactant? f) If the yield of the reaction is 79.9 %, what is the actual yield of Cl2? Show all your work for full credit. Use the correct number of significant figures.

Calculate the enthalpy change for the following reaction: 2Hg(l) + Cl2(g) → Hg2Cl2(s)  ∆H = ? Given the following reactions and their ∆H values: HgCl2(s) → Hg(l) + Cl2(g)  ∆H = 224.0 kJ Hg(l) + HgCl2(s) → Hg2Cl2(g) ∆H = -41.2 kJ

An unknown substance has a mass of 6.40 g. The temperature of the substance increases from 27.1oC to 42.7oC when 89.1 J of heat is added to the substance. Substance Specific Heat (J/g·°C) Lead 0.130 Silver 0.240 Copper 0.385 Iron 0.442 Aluminum 0.892 Water 4.184   a) What is the specific heat of the unknown substance ? [a] J/goC b) Based on the substances shown on the table above, what is the most likely identity of the unknown substance ?[b]

A 125 gram sample of an unknown metal at 95.0oC is placed in 145 gram of water at 25.0oC. If the final temperature of the metal and water is 31.8oC, what is the specific heat capacity of the metal?  (the specific heat of water is 4.184 J/goC). Show all your work for full credit. Use the correct number of significant figures.

How many milliliters of 12.0 M HCl(aq) are needed to prepare 0.745 L of 1.00 M HCl(aq) ?

In the fermentation process, yeast converts glucose to ethanol and carbon dioxide. What volume of carbon dioxide, measured at 745 torr and 25.0°C, can be produced by the fermentation of 32.0 g of glucose? C6H12O6(aq)  → 2C2H5OH(aq)   + 2CO2(g)

Calculate the molar mass of a gas if 0.507 g of this gas occupies 0.250 L at 0.955 atm and 297 K. Show all your work for full credit. Use the correct number of significant figures.

An antacid tablet contains NaHCO3. What mass of this compound is required to neutralize 105 mL of 2.75 M HCl? NaHCO3(aq) + HCl(aq) → NaCl(aq) + CO2(g) + H2O(l)

Calculate the enthalpy change for the following reaction: N2(g) + 2O2(g) → 2NO2(g) ∆H = ? Given the following reactions and their ∆H values: N2(g) + O2(g) → 2NO(g) ∆H = 180.5 kJ 2NO2(g) → 2NO(g) + O2(g) ∆H = 114.12 kJ