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Roman55 [17]
3 years ago
7

Examples of elements​

Chemistry
1 answer:
DedPeter [7]3 years ago
5 0
Oxygen, carbon, hydrogen, nitrogen, aluminum
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After the first steps in writing an equation, the equation is balanced by
kifflom [539]

Answer:

law of conservation of mass

Explanation:

self explanatory

5 0
3 years ago
Technetium-99 is an ideal radioisotope for scanning organs because it has a half-life of 6.0 h and is a pure gamma emitter. supp
Nadusha1986 [10]

Answer: 20 mg Te-99 remains after 12 hours.

Explanation:  N(t) = N(0)*(1/2)^(t/t1/2)

                        N(t) = (80 mg)*(0.5)^(12/6)

N(t) = 20 mg remains after 12 hours

3 0
2 years ago
A nuclear reactor core must stay at or below 95 °C to remain in good working condition. Cool water at a temperature of 10 °C is
aliina [53]

Answer:

\large \boxed{\text{67 000 g}}

Explanation:

This is a problem in calorimetry — the measurement of the quantities of heat that flow from one object to another.

It is based on the Law of Conservation of Energy — Energy can be transformed from one type to another, but it cannot be destroyed or created.

If heat flows out of the reactor (negative), the same amount of heat must flow into the water (positive).

Since there is no change in total energy,

heat₁ + heat₂ = 0

The symbol for the quantity of heat transferred is q, so we can rewrite the word equation as

q₁ + q₂  = 0

The formula for the heat absorbed or released by an object is

 q = mCΔT, where

 m = the mass of the sample

  C = the specific heat capacity of the sample, and

ΔT = T_f - T_i = the change in temperature

1. Equation

There are two heat flows in this problem,

heat released by reactor + heat absorbed by water = 0

               q₁                  +                        q₂                     = 0

               q₁                  +                 m₂C₂ΔT₂                 = 0

2. Data:

q₁ = -23 746 kJ

m₂ = ?; C₂ = 4.184 J°C⁻¹g⁻¹;  T_f = 95 °C; T_i = 10 °C

3. Calculations

(a) Convert kilojoules to joules

q_{1} = -\text{23 746 kJ} \times \dfrac{\text{1000 J}}{\text{1 kJ}} = -\text{23 746 000 J}

(b) ΔT  

ΔT₂ = T_f - T_i = 95 °C - 10 °C = 85 °C

(c) m₂

\begin{array}{rcl}q_{1} + q_{2} & = & 0\\\text{-23 746 000 J} + m_{2} \times 4.184 \text{ J$^{\circ}$C$^{-1}$g$^{-1}$} \times 85 \, ^{\circ}\text{C} & = & 0\\\text{-23 746 000 J} + 356m_{2} \text{J$\cdot$g}^{-1} & = & 0\\356m_{2} \text{g}^{-1} & = & 23746000\\m_2&=& \dfrac{23746000}{\text{356 g}^{-1}}\\\\ & = & \textbf{67000 g}\\\end{array}\\

\text{You must circulate $\large \boxed{\textbf{67 000 g}}$ of water each hour.}

7 0
3 years ago
How many parts per million of fluoride in a solution that is 500 grams of fluoride and 500,000 liters water
erik [133]

0.000001‬ppm

Explanation:

Mass of fluoride = 500g

Volume of water = 500000liters

Unknown:

Parts per million of fluoride = ?

Solution:

The parts per million is the amount of solute in milligram dissolved in a liter of water or milligram per kilogram of solvent

It is a unit used to express very small concentration.

 we need to convert g - mg

   500g = 500 x  10⁻³mg  = 0.5mg

   Concentration in parts per million = \frac{mass in mg}{Volume in liters}

Concentration in parts per million = \frac{0.5}{500000} = 0.000001‬ppm

learn more:

Parts per million brainly.com/question/2854033

#learnwithBrainly

7 0
3 years ago
igneous rock that cools very quickly when it forms may have a texture that is______and______with no visible____
Fudgin [204]
<span>Igneous rock that cools very quickly when it forms may have a texture that is smooth and shiny with no visible grain.</span>
6 0
3 years ago
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