Chapter 7 Random
Explain the difference between the excess and limiting reactants.
Excess reactants are not fully consumed in a chemical reaction and have some amount left over.
The limiting reactant runs out and is fully consumed in a chemical reaction.
4FeO(s) + O2(g) -> 2Fe2O3(s) H= -560kJ
Is the reaction above endothermic or exothermic? Explain how you know.
The reaction is exothermic because the negative enthalpy indicates energy is released.
Calculate the mass in grams of 0.0598 moles of CrF3.
6.52g CrF3
1) 36.8g Ag
2) 76.7%
What is an endothermic process and what sign can we identify them with?
A reaction that absorbs heat from its surroundings
Identified with a positive enthalpy
What is the percent mass of each element in CrF3?
Cr: 47.71%
F: 52.29%
E= -0.7J
What is the molar mass of calcium nitrate?
164.10 g/mol
Determine the limiting reactant of the following equations, given that 1.658 moles of chromium react with 2.225 moles of copper (II) chloride.
2Cr +3CuCl2 --> 2CrCl3 + 3Cu
CuCl2 is the limiting reactant
The change in energy of a system that absorbs 12.4J of heat and does 4.2J of work on the surroundings is ____J.
8.2J
A compound made of 68.2% magnesium and 31.8% oxygen. What is the mass of magnesium in 12.5g of the compound?
8.53g Mg
A chemist places a 20.0g sample of ethanol inside a bomb calorimeter with a known heat capacity of 28.72kJ/degrees C. When the ethanol ignites, the temperature of the calorimeter rises from 22.04 to 42.74 degrees Celcius. How much heat did the ethanol release? Calculate the energy released in kilojoules per gram of ethanol.
-29.7 kJ/g
One mole of potassium sulfate contains how many moles of oxygen?
4 moles of oxygen
2K + Cl2 -> 2KCl
How many grams of KCl are produced from 2.50g of K and excess Cl2?
4.77g KCl
What is the specific heat (J/g*Celcius) of a metal object whose temperature increases by 3.0 degrees celcius when 17.5g of metal was heated with 38.5J?
0.73 J/g*C
How many grams of chlorine are present in 35.87g of aluminum chlorate?
13.76g Cl
Consider the melting of ice:
H2O(s) --> H2O (l) H=44.0 kJ/mol
How much energy is required to melt 55.78g of ice?
136.3 kJ
Determine the number of Cr3+ ions and F- ions in 4.5 mol of CrF3
Cr3+:2.7x1024 ions
F-: 5.1x1024 ions
Given the following equation: 2C4H10 + 13 O2 -> 8CO2 + 10H2O, how many moles of (1) CO2 and of (2) H2O will form when 1.95 moles of C4H10 react with oxygen?
1) 7.80 moles CO2
2)9.75 moles H2O
C2H6O + 3O2 --> 2CO2 +3H2O Hrxn= -1,368kJ
How much energy is produced when 155.6g of ethanol react?
-4,620kJ of ethanol
An iron ore sample is found to be 35.00% Fe by mass. How many grams of ore are needed to obtain 454.0 grams of Fe?
1297 grams of ore
It requires 44.0kJ of energy to turn 1 mole of water into steam (vaporize water) at 100 degrees Celcius. (1)How much energy would it take to vaporize 34.6g of water? (2)If the energy to vaporize the water in part (1) at 100 degrees Celcius is transferred from a block of aluminum (specific heat=0.902 J/g*C) initially at 500 degrees Celsius, what mass of aluminum would be needed? (assume all energy is lost by aluminum vaporizing the water.)
1) 84.5kJ
2) 234g Al
Given the following equation: 2NaClO3 -> 2NaCl + 3O2
How many grams of NaCl are produced when 80.0 grams of O2 are produced?
97.4g NaCl
Given the following equation: 2NiS2 + 5O2 -> 2NiO + 4SO2, (1)how many grams of sulfur dioxide will be produced from the reactions of 25.6g of nickel (IV) sulfide with 35.6g of oxygen gas? (2)How many grams of the excess reactant will remain?
1) 26.7g SO2
2) 18.9g left
A 10.4g sample of NH4Cl was dissolved into 100.0g of water in a coffee cup calorimeter, causing the water temperature to decrease by 6.20 degrees Celsius. Based on this, how much heat energy was required to dissolve the sample of NH4Cl? Calculate the heat of solution for NH4Cl in kJ/mol.
14.8 kJ/mol