Answer:
d. Radon-222
Explanation:
²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He
Alpha particle is a helium nucleus with mass number 4 and atomic number 2. According to the law of conversation of mass, the sum of the mass number and atomic number must be equal on both side of the reaction.
Since the mass number of Ra is 226 and that of He is 4. The mass number of the unknown element must be 226 - 4 = 222.
Since the atomic number of Ra is 88 and that of He is 2. The atomic number of the unknown element must be 88 - 2 = 86.
Now looking in the periodic table Radon is the only element with atomic number 86.
Explanation:
The given cell reaction is as follows.
Hence, reactions taking place at the cathode and anode are as follows.
At anode ; Oxidation-half reaction : 
...... (1)
At cathode; Reduction-half reaction : 
....... (2)
Hence, balance the half reactions by multiplying equation (1) by 2 and equation (2) by 3.
Therefore, net cell reaction is as follows.
Net reaction: 
Thus, we can conclude that the overall cell reaction is as follows.
Answer:
about 0.9 mol
Explanation:
there are 22.990 g/mol of Na
20.7/22.99 = 0.900391 mol
about 0.9 mol
If each gas sample has the same temperature and pressure, which has the greatest volume? Since hydrogen gas has the lowest molar mass of the set, 1 g will have the greatest number of moles and therefore the greatest volume. What is the Ideal Gas Law?
Speed and velocity is a scalar and vector quantity of a similar parameter, respectively. They both refer to how fast an object moves. However, the speed only has to do with the magnitude. The velocity takes into account the sign which indicates the direction of the movement. For example, the value is -5 m/s. The speed is 5 m/s, but the velocity is 5 m/s moving downwards because the negative sign denotes downward movement or movement to the left.
