Answer:
40%
Explanation:
We'll begin by obtaining the molar mass of MgO. This is illustrated below:
Molar Mass of MgO = 24 + 16 = 40g/mol
Observing the formula MgO, we have 1 atom of O in it.
The percentage composition by mass of oxygen in MgO is given by:
Mass of O/Molar Mass of MgO x 100
= 16/40 x 100 = 40%
Answer: Option (d) is the correct answer.
Explanation:
Atomic number of carbon is 6 and its electronic distribution is 2, 4. Therefore, in order to become stable and completely fill its octet carbon readily share its valence electrons with another atom.
For example, 
A carbon atom is also able to form a double double with valence electrons of other atom.
Thus, we can conclude that a carbon atom has a strong tendency to share electrons.
Answer:
You cannot make observations if you are 57 seconds late into the lab.
Explanation:
The atomic nucleus can split by decay into 2 or more particles as a result of the instability of its atomic nucleus due to the fact that radioactive elements possess an unstable atomic nucleus.
Now, the primary particles which are emitted by radioactive elements in order to make them decay are alpha, beta & gamma particles.
The half life equation is;
N_t = N₀(½)^(t/t_½)
Where:
t = duration of decay
t_½ = half-life
N₀ = number of radioactive atoms initially
N_t = number of radioactive atoms remaining after decay over time t
We are given;
t = 57 secs
N₀ = 100 g
Now, half life of Nitrogen-16 from online sources is 7.2 seconds. t_½ = 7.2
Thus;
N_t = 100(1/2)^(57/7.2)
N_t = 0.4139g
We are told that In order to make observations, you require at least .5g of material.
The value of N_t you got is less than 0.5g, therefore you cannot make observations if you are 57 seconds late.
The answer is accuracy.
That is when a test instrument is calibrated, its accuracy is improved. That is the result comes more close to what it is.
The other factor will not be improved that is its reliability and precision remains the same.
So the answer is accuracy is improved when a test instrument is calibrated.
