Answer:
Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g
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Step by step explanation;
Answer:
12g
Step-by-step explanation:
<span><span><span><span>3/4</span>x</span>+11 </span>< <span><span>0.3x</span>+<span>3/4
</span></span></span>First turn 3/4 from both sides to decimals to get..
.75x+11 < 0.3x+.75
And then subtract 0.3x from both sides to get
.45x+11 < .75
And then subtract 11 from both sides to get
.45x < -10.25
And then divide both sides by .45x to get
x < -22.77777778