phys ch 20 questions

In the chemical equation C6H12O6 + 3O2 ⇒ 3CO2 + 6H2O, how many oxygen atoms are on the right side of the equation? 3 7 8 12

12

In the equation C2H4 + 3O2 = ? CO2 + 2H2O, how many CO2 molecules are needed to balance the equation? 1 2 3 4 5

2

Which of the equations below is balanced correctly? 2Zn + O2 ⇒ ZnO Mg + N2 ⇒ MgN3 CH4 +2O2 ⇒ CO2 + 2H2O 2C + O2 ⇒2CO2 2P2 + O2 ⇒ P2O5

CH4 +2O2 ⇒ CO2 + 2H2O

How does a catalyst affect a reaction? It lowers the activation energy. It changes anti-bonding orbitals into bonding orbitals. It raises the activation entropy. It increases the energy of the transition state. It lowers the band gap.

It lowers the activation energy.

In a bonding orbital between two atoms, where is the electron density the highest? (Where do you have the highest probability of detecting an electron?) in between the two atoms around the outside of the two atoms. the density is evenly distributed around both atoms

in between the two atoms

Which of the following is the best description of activation energy? the energy that must be taken out of a system before a reaction can take place the energy at which the forward and reverse reaction rates are equal the energy that is released when a molecular orbital forms the energy that must be put into a system before a reaction can take place.

the energy that must be put into a system before a reaction can take place.

In order for an energetically favorable chemical reaction to occur entropy must increase as a result of the reaction. energy must decrease as a result of the reaction. energy and entropy must both decrease. energy and entropy must both increase. energy must decrease and entropy must increase.

?

In which of the following processes is the end product more ordered than the reactants? (In which process does entropy decrease in the system?) 2C7H5N3O6 (solid) = 3N2 (gas) + 7CO(gas) + 5H2O (gas) + 7 C (solid) 2H2 (gas) + O2 (gas) = 2 H2O (gas) C6H12O6 (solid) + 6O2 (gas) = 6CO2 (gas) + 6H2O (liquid) NaHCO3 (solid) + C2H4O2 (liquid)=C2H3NaO2 (solid)+ H2O(liquid) + CO2 (gas) 2C8H18 (liquid) + 25O2 (gas) = 16CO2 (gas) + 18H2O (gas)

2H2 (gas) + O2 (gas) = 2 H2O (gas)

A very fast reaction has a very high activation energy. True False

False

Energy and entropy are both involved in chemical reactions. True False

True

Molecular orbitals are the same shape as atomic orbitals. True False

False