chemistry questions

2009-04-23 3:31 pm

1. what occurs when an atom of chkorine and an atom of hydrogen become a molecule of hydrogen chloride?
a) a chemical bond is broken and energy is released
b) a chemical bond is broken and energy is absorbed
c) a chemical bond is formed and energy is released
d) a chemical bond is formed and energy is absorbed

2. The stability of an isotope is based on its
a) number of neutrons, only
b) number of protons, only
c) ratio of neutrons to protons
d) ration of electron to protons

3. the relationship between pressure and volume for an ideal gas?

4. which equation shows conservation of both mass and charge?
a)Cl2+Br- --> Cl- +Br2
b) Cu + 2Ag+ --> Cu2+ + Ag
c) Zn + Cr 3+ --> Zn 2+ + Cr
d) Ni + Pb2+ --> Ni2+ + Pb

please explain in details. thank you

回答 (1)

bean_bottom_2

2009-04-24 6:16 pm

✔ 最佳答案

Q1. Answer is c

The product is a molecule of HCl formed from a single atom of Cl and an atom of H. There is no bonds broken but a new bond is formed. The reaction is exothermic and thus gives out heat.

Q2. Answer is c

Stability of an isotope here means the stability of the nucleus. The nucleus of an atom may emit energy or particles in order to evolve into a more stable ratio of proton to neutron.

Q3. The ideal gas law governs the relationships between pressure, temperature and volume for an ideal gas. Note that when temperature is constant, pressure and volume can be described by Boyle's law.

Q4. Answer is
a) is incorrect due to the fact that the number of Cl and Br do not balance. 2 Cl on the left but 1 on the right. 1 Br on the left but 2 Br on the right.
b) is incorrect due to the fact that the number of Ag on the left is 2 but the number of Ag on the right is 1.
c) is incorrect due to the fact that charges are not conserved. There is 3+ on the left and 2+ on the right.
d) is correct. Both number of ions, atoms involved on the left and the right are the same. Also, the charges on the left is 2+ which is the same as the charges on the right.

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