CHEMISTRY HIGH SCHOOL

Starting with 100 grams of uranium-238, after one half life has gone by, how many grams of uranium-238 will remain?A._12.5 grams
B._25 grams
C._50 grams
D._100 grams

Answers

Answer 1

Answer:

Answer : The correct option is, (C) 50 grams

Solution :

Formula used :

$a=(a_o)/(2^n)$

where,

a = amount of reactant left after n-half lives = ?

$a_o$ = Initial amount of the reactant = 100 g

n = number of half lives = 1

Putting values in above equation, we get:

$a=(100)/(2^1)$

$a=50g$

Therefore, the amount of uranium-238 remain will be, 50 g

Answer 2

Answer: Answer C, 50 grams.
This is because a half life is the time it takes for a sample of an unstable isotope to spontaneously so that half of the original sample remains

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If i add water to 100 mL of a 0.15M NaOH solution until the final volume 150mL , what will the molarity of the diluted solution be ?

Which of the following is not equal to 0.536 kilometers? 53.6 hectometers (hm) 536 meters (m) 536,000 millimeters (mm) 53,600 centimeters (cm)

Answers

Answer:

53.6 hectometers

Explanation:

In this case, we have to write out of given options which is not equivalent to 0.536 kilometers.

1 kilometers = 1000 m

So, 0.536 kilometers = 536 meters

1 kilometers = 1000000 millimeters

So, 0.536 kilometers = 536000 millimeters

1 kilometers = 100000 centimeters

0.536 kilometers = 53600 centimeters

And 1 kilometers = 10 hectometers

So, 0.536 kilometers = 5.36 hectometers

Hence, the correct option is (a) " 53.6 hectometers "

I believe it would be 53.6 hectometers, but I'm not 100% sure

A 134.0 g sample of an unknown metal is heated to 91.0⁰C and then placed in 125 g (125 mL) of water at 25.0⁰C. The final temperature of the water is measured at 31.0⁰C. Calculate the specific heat capacity of the unknown metal.

Answers

Answer:

The specific heat capacity of the metal is approximately 0.3903 J/(g·°C)

Explanation:

The mass of the sample of the unknown metal, $m_m$ = 134.0 g

The temperature to which the metal is raised, $t_m$ = 91.0°C

The mass of water into which the mass of metal is placed, $m_w$ = 125 g

The temperature of the water into which the metal is placed, $t_w$ = 25.0°C

The final temperature of the water, $t_f$ = 31.0°C

The specific heat capacity of water, $c_w$ = 4.184 J/(g·°C)

The specific heat capacity of the metal = $c_m$

Therefore, by the first laws of thermodynamics we have;

The heat transferred = Heat supplied by the metal = Heat gained by the water

The heat transferred, ΔQ, is given as follows;

ΔQ = $m_w$ × $c_w$ ×( $t_f$ - $t_w$ ) = $m_m$ × $c_m$ ×( $t_m$ - $t_f$ )

125 × 4.184 × (31 - 25) = 134 × $c_m$ × (91 - 31)

∴ $c_m$ = (125 × 4.184 × (31 - 25))/(134 × (91 - 31)) ≈ 0.3903 J/(g·°C)

The specific heat capacity of the metal = $c_m$ ≈ 0.3903 J/(g·°C)

Which expression represents a reaction rate?a. time/massc. energy/timeb. number/timed. time/energy

Answers

The right answer for the question that is being asked and shown above is that: "b. number/timed." Reaction Rate refers to the speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow are action takes place.

A reaction rate is typically expressed as the change in the amount of reactants or products over a certain period of time. So the option b is correct.

The rate of a chemical reaction can be measured by monitoring the number of moles or molecules of a particular substance consumed or produced per unit of time. Hence, the expression "number/time" best represents a reaction rate. For example, if we observe the formation of 5 moles of product X in 2 minutes, the reaction rate of X would be 5 moles per 2 minutes (5 moles/2 minutes). This quantitative approach allows scientists to study reaction kinetics and understand the speed at which reactions proceed, enabling the optimization and control of various chemical processes. Hence option b is correct.

To know more about reaction rate, here

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Given the reaction: S(s)+ O2(g)- SO2(g)+ energy which diagram best represents the potential energy changes for this reaction

Answers

Its graph 1 I just took the test :)

In an exothermic energy diagram, the reactants side is higher in energy than the product side.

What is an exothermic reaction?

An exothermic reaction is one in which the heat of the reactants is greater than that of the products. In that case, energy is given off in the reaction as heat and the reaction vessel is warmer.

Now, in an exothermic energy diagram, the reactants side is higher in energy than the product side.

Learn more about exothermic reaction:brainly.com/question/12786977

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according to the third law if a football player hits another player with an action force of 1500n how much will the reaction force be

Answers

Answer:

The reaction would be 1500n (equal reaction)

Explanation:

This can be explained by Newton's third law of motion which states that for every action (force), there is an opposite and equal reaction. In other words, when two objects or people come in contact, the magnitude of force which they exert on each other is equal and they both feel an equal reaction force.

It doesn't matter whether one of the colliding bodies is of bigger mass than the other. This Newton's third law of motion is also known as the law of action and reaction.

When does phenolphthalein turn pink?a) in the presence of a base

b) in the presence of an acid

c) when it is in a neutral solution

d) when it is reacting with a metal

Answers

Answer is: a) in the presence of a base.

Phenolphthalein is colorless in acidic solutions and pink in basic solutions.

Acid-base indicators are usually weak acids or bases and they are chemical detectors for hydrogen or hydronium cations.

Example for acid-base indicator is phenolphthalein (molecular formula C₂₀H₁₄O₄).

When solution turns phenolphthalein pink, it means it is basic (pH>7).

Final answer:

Phenolphthalein turns pink in the presence of a base.

Explanation:

Phenolphthalein turns pink in the presence of a base. It is a pH indicator that changes color depending on the acidity or alkalinity of a solution. In an acidic solution, phenolphthalein remains colorless, while in a basic solution, it turns pink.