Answer:b.CaCl2
Explanation:
A compound is a substance resulting when two or more elements are are chemically bonded together either ionically or covalently in a fixed ratio.
From the given options we can see that the only compound there is CaCl2 which is an ionic compound in the fixed ratio of one calcium ion to two chloride ions.
Other options , Cu,Na and Nd are merely pure substance---Elements
Explanation:
The given data is as follows.
= 98.70 kPa = 98700 Pa,
T =
= (30 + 273) K = 303 K
height (h) = 30 mm = 0.03 m (as 1 m = 100 mm)
Density = 13.534 g/mL = 
= 13534 
The relation between pressure and atmospheric pressure is as follows.
P = 
Putting the given values into the above formula as follows.
P = 
= 
= 102683.05 Pa
= 102.68 kPa
thus, we can conclude that the pressure of the given methane gas is 102.68 kPa.
For which of the following activities might you want to hire a chemist?
Answer: D. testing a rock sample for gold content
Which of the following procedures involves a physical change in one of the substances?
Answer: C. separating a salt solution by evaporating the water
Explanation:
elctronic configuration of manganese
Mn=1s²2s²2p⁶3s²3p⁶4s²3d⁵
ground state
Mn=Ar3d⁵4s²
note that Ar is argon