Heat Reactions
A Chemist measures the energy change in Delta H during the following reaction.
Cl2 (g)+H2(g)--> 2HCl(g)
Delta H = -155.8 kJ
Is this reaction endothermic or exothermic?
exothermic
The vapor pressure of methanol at 25 degrees C is 138 torr. Calculate the vapor pressure in atm.
.182 atm
What is the percent yield of NaCl if the actual yield is 9.89 grams and the theoretical yield is 22.8 grams?
43.38%
What is the molecular shape of water?
bent
How many valence electrons are in Gallium?
3
Calculate the energy required to head 340.4 mg of warer from 54.8 degrees C to 60.0 degrees C. Assume a specific heat capacity of water under these conditions is 4.18 J*g-1*K-1. Round to 2 sig figs.
7.4 kJ
The atmospheric pressyre in La Paz, the capitol of Bolivia (3627 m elevation) is .632 atm. Calculate the atmospheric pressure in mmHg to 3 sig figs.
.000832 mmHg
Aqueous hydrobromic acid (HBr) will react with sodium hydroxide (NaOH) to produce aqueous sodium bromide (NaBr) and liquid water.
HBr + NaOH --> NaBr + H2O
Suppose 1.2 grams of HBr is mixed with .65 g of NaOH. Find the maximum mass of NaBr that could be produced by the chemical reaction. Round to 3 sig figs.
1.53g NaBr
Draw the Lewis structure for CO2
on board
Rank these atoms in order of increasing size.
Ac, He, Nb, Ra
He<Nb<Ra<Ac
Find the energy required to to heat 90 mg of graphite from 3.0 degrees C to 20.9 degrees C. Assume a specific heat capacity of .710 J*g-1*K-1. Round to 3 Sig figs.
1.14 kJ
For many purposes we can treat propane (C3H8) as an ideal gas at temperatures above its boiling point of -42.0 degrees C.
Suppose the temperature of a sample of propane gas is raised from -16 degrees C to 18 degrees C, and at the same time the pressure is changed. If the initial pressure was 3.2 atm and the volume increased by 33%, what is the final pressure? Round to 2 sig figs
2.7 atm
Ammonium Phospate ((NH4)3PO4) is an ingredient found in many fertilizers. It can be made by reacting phosphoric acid (H3PO4) with ammonia (NH3).
What mass if ammonium phosphate is produced by the reaction of 4.3 g of phosphoric acid?
6.542g ammonium phosphate
Is ethanol (C2H6O) polar or non polar?
polar
Write the electron configuration for a neutral atom of Calcium.
[Ar]4s2 OR 1s22s22p63s23p64s2
A chemical reaction takes place inside a flask submerged in a water bath. The water bath contains 1.0 Kg of water at 32.67 degrees C. During the reaction of 134 kJ of heat flows out of the bath and into the flask.
Calculate the new temperature of the water bath. You can assume the specific heat capacity of water under these conditions is 4.18 J*g-1*K-1. Round your answer to 3 significant digits.
32.7 degrees C
A diver is preparing a deep sea sumbersible for a dive. The sub stores breathing air under high pressure in a cylinder that measures 66.9 cm wide and 34.2 cm high.
The diver estimates she will need 4000.0 L of air for the dive. Find the pressure to which this volume of air must be compressed to fit in the air tank in atmospheres to 3 sig figs.
33.3 atm
Gaseous butane (CH3(CH2)2CH3) reacts with O2 to form carbon dioxide and water. What is the Theoretical Yield of carbon dioxide formed from the reaction of 5.45 grams of butane and 13.77 grams of oxygen gas.
11.653g CO2
What word/words best decribe the shape of NH4+?
tetrahedral
Re-order this list of atoms so they are listed in order of decreasing electronegativity
Li,C,Br,Rh
Br>C>Rh>Li
A Chemist meausres delta H in the following reaction.
2H2O(l)-->2H2(g)+O2(g)
Delta H = 602 kJ
Determine if the reaction is endothermic or exothermic. If 60.3 grams of water react, will any heat be released or absorbed? If so calculate how much heat will be released or absorbed to 3 sig figs.
endothermic, 1010 kJ
Suppose .45 kg of nonane (C9H20) are burned in air at a pressure of exactly 1 atm and a temperature of 12 degrees C. Write the chemical equation for the combustion of nonane into carbon dioxide and water. Find the Volume of CO2 gas that is produced.
C9H20 + 14O2 --> 9CO2 + 10H2O
738.485 L
Methane (CH4) reacts with O2 to produce CO2 and water. What is the theoretical yield of water formed from the reaction of 2.19 g of methane and 22.0 grams of oxygen gas? Give the answer in 3 significant figures.
4.92 g water
Draw the Lewis Structure for CCl4. Then, count the number of lone pairs in the structure.
12 (24 electrons)
Write the electron configuration for a beryllium anion with a charge of 2-.
1s22s22p2