Answer:
Explanation:
Isotopes are atoms of elements that have the same atomic number but different mass number hence ISOTOPY. Radioactive Isotopes on the other hand are unstable as they either undergo Alpha decay, beta decay or gamma decay compared to stable isotopes.
Radioactive elements decay at varyinf rates as such the rate of radioactive decay is used in the characterization of radioactive element and mostly expressed in terms of the half life of the radioactive elements.
Half life is the time taken for half of the total atoms of an elements to decay into half of its initial sizes. for example, the half life of radium-226 is 1622 years, it implies that if we have 1000000 radium atoms at the beginning, then at the end of 1622years, 500000 would have disintegrated. These phenomenon can never be experienced by stable isotopes as such they can not be used in carbon dating techniques. reason why uranium-238 is mostly and commonly used in the earth crust to estimate the ages of rocks because it has a half life of 4.5 x 10^9 years.
And also, the radioactive isotopes of most common light element are short, they have very short half life (few days or weeks) and they decay rapidly to vanshing point, as such, they are not found in nature to any reasonable extent.
Correct Answer: <span>compound because the atoms of the elements are combined in a fixed proportion.
Reason:
A </span><span> chemical </span>compound is a chemical substance composed of element (of same or different type) that are bonded in a fixed proportion. Depending upon the type of element, bond can be ionic or covalent. In present case, <span>tetrachloromethane i.e. CCl4 has one 'C' atom that is covalently bonded to four 'Cl' atoms. </span>
Jayne's science teacher mixed a clear liquid with a blue liquid in a beaker. After a few minutes there was a white solid at the bottom of the beaker.So,<span>It is a new substance with different properties.</span>
Answer: Option A) 83.9g
Explanation:
KCl is the chemical formula of potassium chloride.
Given that,
Amount of moles of KCl (n) = ?
Volume of KCl solution (v) = 0.75L
Concentration of KCl solution (c) = 1.5M
Since concentration (c) is obtained by dividing the amount of solute dissolved by the volume of solvent, hence
c = n / v
make n the subject formula
n = c x v
n = 1.5M x 0.75L
n = 1.125 mole
Now given that,
Amount of moles of KCl (n) = 1.125
Mass of KCl in grams = ?
For molar mass of KCl, use the molar masses of:
Potassium, K = 39g;
Chlorine,Cl = 35.5g
KCl = (39g + 35.5g)
= 74.5g/mol
Since, amount of moles = mass in grams / molar mass
1.125 mole = m / 74.5g/mol
m = 1.125 mole x 74.5g/mol
m = 83.81g
Thus, 83.9 grams of KCl are needed to prepare 0.750 L of a 1.50 M solution in water
Answer:
Explanation:
Hello,
In this case, for the calculation of the pH of the given buffer we need to use the Henderson-Hasselbach equation:
![pH=pKa+log(\frac{[base]}{[acid]} )](https://tex.z-dn.net/?f=pH%3DpKa%2Blog%28%5Cfrac%7B%5Bbase%5D%7D%7B%5Bacid%5D%7D%20%29)
Whereas the pKa for benzoic acid is 4.19, the concentration of the base is 0.15 M (sodium benzoate) and the concentration of the acid is 0.25 M (benzoic acid), therefore, the pH turns out:
Regards.
