A membrane Is a flexible outer layer found on:

When HBr combines with water, it produces H3O+ and Br- ions. This shows that HBr is a base. true false

ELEN [110]

HBr is a strong acid

False

6 0

3 years ago

Notice in the picture of sedimentary rocks, there is one layer on top of the other. The oldest rocks are on the bottom of the pi

amm1812

Answer:

A. Superposition

Explanation:

A law of geochronology, stating that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it.

3 0

3 years ago

How many molecules of hydrogen gas (Hz) are needed to produce 9.0 x 1023 molecules of H2O?

VashaNatasha [74]

Answer:

Explanation: Ammonia (NH3) is produced by the reaction of nitrogen gas and hydrogen gas. ... How many grams of fluorine gas are needed to produce 100.00g of AlF3? ... How many molecules of CO2 gas can be produced of 156.24g of benzene, ... (a) If 16.74.g of Fe and 9.0 9 of H2O are allowed to react, how many grams of products.

4 0

3 years ago

A certain radioactive isotope decays at a rate of 0.2% annually. Determine the half-life of this isotope, to the nearest year

pychu [463]

Answer:

The half-life of the radioactive isotope is 346 years.

Explanation:

The decay rate of the isotope is modelled after the following first-order linear ordinary differential equation:

$\frac{dm}{dt} = -\frac{m}{\tau}$

Where:

$m$ - Current isotope mass, measured in kilograms.

$t$ - Time, measured in years.

$\tau$ - Time constant, measured in years.

The solution of this differential equation is:

$m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }$

Where $m_{o}$ is the initial mass of the isotope. It is known that radioactive isotope decays at a yearly rate of 0.2 % annually, then, the following relationship is obtained:

$\%e = \frac{m(t)-m(t+1)}{m(t)}\times 100\,\% = 0.2\,\%$

$1 - \frac{m(t+1)}{m(t)} = 0.002$

$1 - \frac{m_{o}\cdot e^{-\frac{t+1}{\tau} }}{m_{o}\cdot e^{-\frac{t}{\tau} }}=0.002$

$1 - e^{-\frac{1}{\tau} } = 0.002$

$e^{-\frac{1}{\tau} } = 0.998$

$-\frac{1}{\tau} = \ln 0.998$

The time constant associated to the decay is:

$\tau = -\frac{1}{\ln 0.998}$

$\tau \approx 499.500\,years$

Finally, the half-life of the isotope as a function of time constant is given by the expression described below:

$t_{1/2} = \tau \cdot \ln 2$

If $\tau \approx 499.500\,years$ , the half-life of the isotope is:

$t_{1/2} = (499.500\,years)\cdot \ln 2$

$t_{1/2}\approx 346.227\,years$

The half-life of the radioactive isotope is 346 years.

6 0

3 years ago

What is the 10% energy rule?

Brut [27]

<span>What is the 10% energy rule?</span>

The 10% energy rule means that when energy is passed into the ecosystem from one trophic level into the next, only ten percent energy will be passed on.

5 0

3 years ago