Half-life is the time required for decay of 50% of radio-active nuclei.
Thus, when radio-active material crosses 1st half-life, 100/2 = 50% radio-active material is left and remaining 50% is elapsed.
When, when radio-active material crosses 2nd half-life, 50/2 = 25% radio-active material is left and remaining 75% is elapsed.
When radio-active material crosses 3rd half-life, 25/2 = 12.5% radio-active material is left and remaining 87.5% is elapsed.
Thus, 2 <span>half-lives must elapse until 84 % of a radioactive sample of atoms has decayed.</span>
Answer:
Na < K < S < Be
Explanation:
Let's work with NA and molar mass of each.
- 1.5 mol of K → should be converted to atoms ( mol . NA)
1.5 mol . 6.02×10²³ = 9.03×10²³ atoms of K
- 64 g of S → should be converted to mol (mass / molar mass). Then, into atoms. (mol . NA)
64 g / 32.06 g/m = 1.99 mol
1.99 m . 6.02×10²³ = 1.20×10²⁴ atoms of S
- 20 g of Be → should be converted to mol (mass / molar mass). Then, into atoms. (mol . NA)
20 g / 9.01 g/m = 2.22 moles
2.22 m . 6.02×10²³ = 1.33×10²⁴ atoms of Be
- 25 g of Na → should be converted to mol (mass / molar mass). Then, into atoms. (mol . NA)
25 g / 23 g/m = 1.08 moles
1.08 m . 6.02×10²³ = 6.54×10²³ atoms of Na
Answer:
Changes in colour of litmus paper.
- Blue litmus turns red under acidic conditions.
- Red litmus turns blue under basic conditions.
Noe
PH values:-
K is acidic as pH is <7
Hence K will change the colour of blue litmus paper.
#B
Examples of substances
- K=Vinegar, Tomatoes.
- M=Milk of magnesia,Soap
Answer:
C. 2&3 created a chemical change
Explanation:
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The answer is: Test
To test a hypothesis you test it with a test to prove if your correct or wrong.
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