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andre [41]
3 years ago
10

Which of the following weighing balances performs measurement in a closed compartment with no air currents to disturb measuremen

t?
Spring balance
Analytical balance
Hydraulic balance
Physics
2 answers:
padilas [110]3 years ago
6 0
Out of the following choices given, hydraulic balances performs measurement in a closed compartment with no air currents to disturb measurement. The correct answer is C. 
ruslelena [56]3 years ago
3 0

Answer: the second option, analytical balance.

Explanation:

Chemical analysis may require very accurate measurements of small samples of matter, and some times that matter is in form of fine powder.

That means that air currents may interfere with the sample, either by dragging part of the sample or by depositing dust over the sample, with which the measure may result not to be as exact as desired to have an analytical result.

An analytical balance is designed to be used in labs to measure small masses with high precision. The weighing pans are inside of a compartment with glass windows which once closed avoid that the air currents to introduce dust or remove some of the sample which would lead to an erroneous measure.

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A certain first-order reaction is 58% complete in 95 s. What are the values of the rate constant and the half-life for this proc
guajiro [1.7K]

Answer:

0.005734 s^{-1} and 20.86 seconds are the values of the rate constant and the half-life for this process respectively..

Explanation:

Expression for rate law for first order kinetics is given by:

a_o=a\times e^{-kt}

where,

k = rate constant  

t = age of sample

a_o = let initial amount of the reactant  

a = amount left after decay process  

We have :

a_o=x

a=58\%\times x=0.58x

t = 95 s

0.58x=x\times e^{-k\times 95 s}

\k= 0.005734 s^{-1}

Half life is given by for first order kinetics::

t_{1/2}=\frac{0.693}{k}

=\frac{0.693}{0.005734 s^{-1}}=120.86 s

0.005734 s^{-1} and 20.86 seconds are the values of the rate constant and the half-life for this process respectively..

3 0
3 years ago
Cesium-137 undergoes beta decay and has a half-life of 30.0 years. How many beta particles are emitted by a 14.0-g sample of ces
Mandarinka [93]

Answer: 0.81\times 10^{16} beta particles

Explanation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

Given mass = 14.0 g

Molar mass = 137 g/mol

\text{Number of moles of cesium}=\frac{14.0g}{137g/mol}=0.102moles

According to avogadro's law, 1 mole of every substance weighs equal to its molecular mass and contains avogadro's number 6.023\times 10^{23} of particles.

1 mole of cesium contains atoms =  6.023\times 10^{23}

0.102 moles of cesium contains atoms =  \frac{6.023\times 10^{23}}{1}\times 0.102=0.614\times 10^{23}

The relation of atoms with time for radioactivbe decay is:

N_t=N_0\times \frac{1}{2}^{\frac{t}{t_{\frac{1}{2}}}}

Where N_t =atoms left undecayed

N_0 = initial atoms

t = time taken for decay = 3 minutes

{t_{\frac{1}{2}}} = half life = 30.0 years = 1.577\times 10^7 minutes

The fraction that decays  :  1-(\frac{1}{2})^{\frac{3}{1.577\times 10^7}}=1.32\times 10^{-7}

Amount of particles that decay is  = 0.614\times 10^{23}\times 1.32\times 10^{-7}=0.81\times 10^{16}

Thus 0.81\times 10^{16} beta particles are emitted by a 14.0-g sample of cesium-137 in three minutes.

7 0
3 years ago
Describe what causes the flow of electric current.
marusya05 [52]
An electrical <span>current is </span>caused<span> by </span>flow<span> of free electrons from one atom to another. </span>
5 0
3 years ago
Read 2 more answers
Find the magnitude of the electric force between the charges 0.12 C and 0.33 C at a separation of 2.5 m. k=8.99×109N⋅m2/C2.
makkiz [27]

Answer:

F= k Q1 Q2 / r^2

plug in the numbers

8 0
2 years ago
True or false the hotter the star the higher is absolute magnitude?
liubo4ka [24]

Answer:

true

Explanation:

6 0
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