You have 40 grams of Gold-189 which has a half-life of 30 minutes. How much Gold

Question

You have 40 grams of Gold-189 which has a half-life of 30 minutes. How much Gold is there after two hours? a. 80 grams b. 20 grams c. 10 grams d. 2.5 grams e 160 grams 2. You leave an ice-cube (solid H_2O) out on a very HOT day and it melts into water (liquid H_2O) and then evaporates away into vapor (gas H_2O). These changes are an example of a. Cannot determine without knowing the temperature at which the changes occurred. b. Only chemical reactions c. Only physical reactions d. a physical reaction followed by a chemical reaction e. a chemical reaction followed by a physical reaction List the DENSITY of the three states of matter of (H_2O) from highest to lowest density. a. Solid (H_2O) - vapor (H_2O) - liquid (H_2O). b. Liquid (H_2O) - solid (H_2O) - vapor (H_2O). c. Liquid (H_2O) - vapor (H_2O) - solid (H_2O). d. All three states have the same density. e. Solid (H_2O) - liquid(H_2O) - vapor (H_2O). The reaction below would be classified (in an energy) sen

Explanation / Answer

ANSWER No-1- (D)- 2.5 GRAM

All you have to do here is to use the following equation

At=A0*(1/2)n here n is power of 1/2

Here

In your case, you know that the initial mass of the substance is equal to 40g.

Now, the number of half-lives that pass in a given time period t can be calculated by dividing the period of time by the half-life of the substance, t1/2.

n= t/t1/2 here n is equal to t by t half.

In your case, the number of half-lives that pass in 30 minutes is equal to

n= 2hour/30 minute

= 2*60minutes/30minute

= 4 minute

Plug this into the aforementioned equation and solve for A30 MINUTES years, the mass of the substance that remains undecayed after 30 MINUTES.

A 30 MIN =40 GRAM *(1/2)4 HERE 4 IS THE POWER OF HALF.

=40/16

=2.5 GRAM.

ANSWER No- 2 (C)- ONLY PHYSICAL REACTION

ANSWER NO-3(c)- LIQUID- VAPOUR- SOLIDS

ANSWER No-4-(b)- Endothermic reaction

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