Choose A, Kr is noble gas
Option B: 4.3
There are following rules for rounding off numbers:
1. If the rounding digit has digit less than 5 (1,2,3 and 4) to its right, all the digits on right side of the rounding digit will drop out.
2. If the rounding digit has digit equal and greater than 5 (5,6,7,8 and 9) to its right, one is added to the rounding digit.
Jeff has to weigh 4.312 g sample of NaCl. To round off the underline number 4.<u>3</u>12, check for the digit right to it. It has 1, which is less than 5 thus according to the Rule 1, all the digits on right side of the rounding digit will drop out and the number gets rounded off to 4.3.
Therefore, 4.3 is most accurate measurement by Jeff.
Answer:
As a catalyst
Explanation:
Concentrated sulfuric acid is used as a catalyst, and has a dual role: Speeds up the reaction. Acts as a dehydrating agent, forcing the equilibrium to the right and resulting in a greater yield of ester.
Answer:
This element is Boron (B) and has an average atomic mass of 10.8109 u
Explanation:
The average mass of an element is calculated by taking the average of the atomic masses of its stable isotopes.
The enitre atomic mass = 100 % or 1
⇒ this consists of 19.91 % atoms with mass 10.01 u
19.91 % = 0.1991
⇒ this consists of 80.09 % atoms with mass 11.01 u
80.09 % = 0.8009
To calculate the mass of this isotope we use the following:
0.1991 * 10.01 + 0.8009 * 11.01 = 10.8109 u
This element is Boron (B) and has an average atomic mass of 10.8109 u
